Active sites of the enzyme is that point where substrate molecule bind for the chemical reaction. It is generally found on the surface of enzyme and in some enzyme it is a “Pit” like structure
The active site is a three-dimensional cleft formed by groups that come from different parts of the amino acid sequence
The active site takes up a relatively small part of the total volume of an enzyme
Active sites are clefts or crevices
Substrates are bound to enzymes by multiple weak attractions.
The specificity of binding depends on the precisely defined arrangement of atoms in an active site.
Enzymes properties, nomenclature and classificationJasmineJuliet
Enzymes - Definition, Introduction about biocatalysts, Properties of enzymes, Specificity, capacity for regulation, Example for enzyme at specific pH, Nomenclature of enzymes, Systematic name, common name, enzyme commission number, Classification of enzymes: Oxidoreductase, Transferase, lyases, ligases, isomerases, hydrolases.
An enzyme is a substance that acts as a catalyst in living organisms, regulating the rate at which chemical reactions proceed without itself being altered in the process. The biological processes that occur within all living organisms are chemical reactions, and most are regulated by enzymes
Active sites of the enzyme is that point where substrate molecule bind for the chemical reaction. It is generally found on the surface of enzyme and in some enzyme it is a “Pit” like structure
The active site is a three-dimensional cleft formed by groups that come from different parts of the amino acid sequence
The active site takes up a relatively small part of the total volume of an enzyme
Active sites are clefts or crevices
Substrates are bound to enzymes by multiple weak attractions.
The specificity of binding depends on the precisely defined arrangement of atoms in an active site.
Enzymes properties, nomenclature and classificationJasmineJuliet
Enzymes - Definition, Introduction about biocatalysts, Properties of enzymes, Specificity, capacity for regulation, Example for enzyme at specific pH, Nomenclature of enzymes, Systematic name, common name, enzyme commission number, Classification of enzymes: Oxidoreductase, Transferase, lyases, ligases, isomerases, hydrolases.
An enzyme is a substance that acts as a catalyst in living organisms, regulating the rate at which chemical reactions proceed without itself being altered in the process. The biological processes that occur within all living organisms are chemical reactions, and most are regulated by enzymes
Introduction, Nomenclature of enzymes, Classification of enzymes on the basis of site of action, on the reaction of catalysis and Classification depends upon substrates on they which act, Specificity of Enzymes, Active Site of An Enzyme: 1. Lock-key model 2. Induce fit model, Factors Affecting Enzymes Reaction, Enzyme 1.Inhibition Competitive inhibition, 2. Non-Competitive inhibition, Isoenzymes, Allosteric Enzymes, Co-Factors, Turnover Number of An Enzyme, Pharmaceutical Importance Of Enzymes,
This ppt describes the overview of enzyme regulation and Allosterism. Presented since October 23,2017GC at Addis Ababa University, School of Medicine, Department of medical biochemistry.
Introduction
Definition
Historical aspects
Nomenclature of enzymes on the basis of
1. Substrate acted
2. Reaction catalyzed
3. substrate act upon and type of reaction catalyzed
Classification of enzymes
Oxidoreductase
Transferase
Hydrolase
Lyase
Isomerase
Ligase
Property of enzyme
Structure of enzyme
Mechanism of enzyme action
Lock and key model
Induced fit model
factors affecting enzyme activity
Control of enzyme action
Conclusion
Reference
Enzymes definitions, types & classificationJasmineJuliet
Enzyme - Introduction, Biocatalysts, Definition of enzymes, Types of enzymes, classification of enzyme, Nomenclature of enzymes, EC number, Types of enzymes with examples, and reaction.
Introduction, Nomenclature of enzymes, Classification of enzymes on the basis of site of action, on the reaction of catalysis and Classification depends upon substrates on they which act, Specificity of Enzymes, Active Site of An Enzyme: 1. Lock-key model 2. Induce fit model, Factors Affecting Enzymes Reaction, Enzyme 1.Inhibition Competitive inhibition, 2. Non-Competitive inhibition, Isoenzymes, Allosteric Enzymes, Co-Factors, Turnover Number of An Enzyme, Pharmaceutical Importance Of Enzymes,
This ppt describes the overview of enzyme regulation and Allosterism. Presented since October 23,2017GC at Addis Ababa University, School of Medicine, Department of medical biochemistry.
Introduction
Definition
Historical aspects
Nomenclature of enzymes on the basis of
1. Substrate acted
2. Reaction catalyzed
3. substrate act upon and type of reaction catalyzed
Classification of enzymes
Oxidoreductase
Transferase
Hydrolase
Lyase
Isomerase
Ligase
Property of enzyme
Structure of enzyme
Mechanism of enzyme action
Lock and key model
Induced fit model
factors affecting enzyme activity
Control of enzyme action
Conclusion
Reference
Enzymes definitions, types & classificationJasmineJuliet
Enzyme - Introduction, Biocatalysts, Definition of enzymes, Types of enzymes, classification of enzyme, Nomenclature of enzymes, EC number, Types of enzymes with examples, and reaction.
Enzymes - A complete introduction and applicationsIndhra Yogaesh
Enzymes are macromolecular biological catalysts. Enzymes accelerate, or catalyze, chemical reactions. The molecules at the beginning of the process are called substrates and the enzyme converts these into different molecules, called products.
This section has been prepared by Worthington Biochemical Corporation as a practical
introduction to enzymology. Because of its close involvement over the years in the theoretical
as well as the practical aspects of enzymology, Worthington's knowledge covers a broad
spectrum of the subject. Some of this information has been assembled here for the benefit of
laboratory personnel.
Enzymes are biological molecules (proteins) that act as catalysts and help complex reactions occur everywhere in life. Let's say you ate a piece of meat. Proteases would go to work and help break down the peptide bonds between the amino acids.
Enzymes are biological molecules (typically proteins) that significantly speed up the rate of virtually all of the chemical reactions that take place within cells. They are vital for life and serve a wide range of important functions in the body, such as aiding in digestion and metabolism
This presentation explores a brief idea about the structural and functional attributes of nucleotides, the structure and function of genetic materials along with the impact of UV rays and pH upon them.
This presentation intends to explore the communication of the cell within and others for sustainability along the regulation mechanisms by the cellular neural networks and others to sing the song of the life.
Bioenergetics is an important domain in biology. This presentation has explored ATP production and its optimum utilization in biological systems along with certain theories and experiments to give a bird's eye view of this important issue.
This presentation offers the bird's eye view of the cell as the basic structural and functional unit of life. It also addresses the origin of eukaryotic cells from the prokaryotic cell by the endosymbiotic theory.
This presentation has been intended to offer a bird's eye view about the phylogenetic classification of the plant kingdom in general and the Engler and Prantl system in particular with merits and demerits.
This PPT has been made to explore the plant classification in general and the classification as made by Bentham & Hooker for the classification of the flowering plants. It also offers the history of plant classification along with the merits and demerits of this aforesaid classification.
Energy and the biological systems are joined together and no biological world is almost impossible without ATP. This study material intends to explore the beauty of ATP to drive different biological processes.
This PPT offers a bird's eye view of ICBN and its different rules along with regulations for the naming of plants. It also highlights the history of IBC and its contribution to plant taxonomy.
This presentation intends to offer the basic features of plant metabolism along with the different types of mechanisms to regulate and control the metabolic pathways.
This presentation has been designed to give the foundation of taxonomy in general and Plant Taxonomy in particular as a matter of pleasure to explore the diversity of the plant world.
Sex and sexuality are very common words in biology but para-sexuality is a little bit uncommon, several organisms in general and fungi in particular have the pleasure of sexuality to bring variations by beside sex. This PPT explores the beauty of para-sexuality for the academic fraternity.
Sex life in fungi is not less fascinating than in other organisms. Heterosexuality is a matter of pleasure to explore the diversity of sex in fungi along with its cause and consequences. You can find a pleasure to go through the content.
This PowerPoint wants to explore the bird's eye view of the reproduction of bacteria in general and the genetic recombination of bacteria in particular.
This presentation gives the bird's eye view of bacterial nutrition along with some other issues required to understand bacterial diversity as far as nutrition is concerned.
This presentation explores the food value of mushrooms along with the long-term and short-term storage procedures. It also offers a detailed account of the nutrients that remain present in the edible mushrooms.
If you want to explore the role of Cyanobacteria in soil fertility in general & Azolla-Anabena association in particular, you can visit this PowerPoint Presentation.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
Slide 1: Title Slide
Extrachromosomal Inheritance
Slide 2: Introduction to Extrachromosomal Inheritance
Definition: Extrachromosomal inheritance refers to the transmission of genetic material that is not found within the nucleus.
Key Components: Involves genes located in mitochondria, chloroplasts, and plasmids.
Slide 3: Mitochondrial Inheritance
Mitochondria: Organelles responsible for energy production.
Mitochondrial DNA (mtDNA): Circular DNA molecule found in mitochondria.
Inheritance Pattern: Maternally inherited, meaning it is passed from mothers to all their offspring.
Diseases: Examples include Leber’s hereditary optic neuropathy (LHON) and mitochondrial myopathy.
Slide 4: Chloroplast Inheritance
Chloroplasts: Organelles responsible for photosynthesis in plants.
Chloroplast DNA (cpDNA): Circular DNA molecule found in chloroplasts.
Inheritance Pattern: Often maternally inherited in most plants, but can vary in some species.
Examples: Variegation in plants, where leaf color patterns are determined by chloroplast DNA.
Slide 5: Plasmid Inheritance
Plasmids: Small, circular DNA molecules found in bacteria and some eukaryotes.
Features: Can carry antibiotic resistance genes and can be transferred between cells through processes like conjugation.
Significance: Important in biotechnology for gene cloning and genetic engineering.
Slide 6: Mechanisms of Extrachromosomal Inheritance
Non-Mendelian Patterns: Do not follow Mendel’s laws of inheritance.
Cytoplasmic Segregation: During cell division, organelles like mitochondria and chloroplasts are randomly distributed to daughter cells.
Heteroplasmy: Presence of more than one type of organellar genome within a cell, leading to variation in expression.
Slide 7: Examples of Extrachromosomal Inheritance
Four O’clock Plant (Mirabilis jalapa): Shows variegated leaves due to different cpDNA in leaf cells.
Petite Mutants in Yeast: Result from mutations in mitochondrial DNA affecting respiration.
Slide 8: Importance of Extrachromosomal Inheritance
Evolution: Provides insight into the evolution of eukaryotic cells.
Medicine: Understanding mitochondrial inheritance helps in diagnosing and treating mitochondrial diseases.
Agriculture: Chloroplast inheritance can be used in plant breeding and genetic modification.
Slide 9: Recent Research and Advances
Gene Editing: Techniques like CRISPR-Cas9 are being used to edit mitochondrial and chloroplast DNA.
Therapies: Development of mitochondrial replacement therapy (MRT) for preventing mitochondrial diseases.
Slide 10: Conclusion
Summary: Extrachromosomal inheritance involves the transmission of genetic material outside the nucleus and plays a crucial role in genetics, medicine, and biotechnology.
Future Directions: Continued research and technological advancements hold promise for new treatments and applications.
Slide 11: Questions and Discussion
Invite Audience: Open the floor for any questions or further discussion on the topic.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
2. Presented by
Dr. N. Sannigrahi, Associate Professor,
Department of Botany,
Nistarini College, Purulia(W.B) India.
3. WHAT IS ENZYME
The term-Enzyme comes from ‘en=in & zyme’=Yeast coined by F.W Kuhn (1878)
Enzymes are a biological substance that accelerates the rate of various biochemical
reactions in a living organism without being used up in the reaction. The actions of
enzymes are specific and biodegradable. Enzymes are involved in most of the
biochemical reactions going on in microorganisms, plants, animals, and human
beings. Even though enzymes are produced inside living cells, they can work
actively in vitro, making them useful in industrial processes.
The assimilation of enzymes in food processing is well known, and devoted research
continues consistently to solve the worldwide food crisis
Enzymes are catalysts that, within the mild conditions of temperature, pH, and
pressure of the cells, carry out chemical reactions at amazing high rate. They are
characterized by a remarkable efficiency and specificity.
Unequivocally called-an orderly function of enzymes
6. NATURE OF ENZYMES
All enzymes are globular proteins with the exception of recently discovered RNA
enzymes( Ribozymes). Some enzymes may additionally contain a non-protein group.
Accordingly there are two types of enzymes, simple and conjugate.
Simple Enzyme: It is an enzyme which is wholly made up of protein. Active site is
formed by specific grouping of its own amino acids. Additional substance or group
is absent, e.g., pepsin, trypsin, unease.
Apoenzyme + Cofactor= Holoenzyme, Cofactor either Coenzyme, Prosthetic group
or Metal activator
It is an enzyme(Complex protein enzyme) which is formed of two parts— a protein
part called apoenzyme (e.g., flavoprotein) and a non-protein part named cofactor.
The complete conjugate enzyme, consisting of an apoenzyme and a cofactor, is
called holoenzyme. Active site is formed jointly by apoenzyme and cofactor.
Cofactor is small, heat stable and dialyzable part of conjugate enzyme. It may be
inorganic or organic in nature. Organic cofactors are of two types, coenzymes and
prosthetic groups.
7. APOENZYME, COENZYME, HOLOENZYME
Coenzymes are easily separable non-protein organic cofactors. Prosthetic groups are
non-protein organic cofactors firmly attached to apoenzymes, e.g., heme (= haem),
biotin, pyridoxal phosphate. Heme (= haem) is iron containing prosthetic group in
cytochromes, hemoglobin, myoglobin, catalase and peroxidase.
The last two cause breakdown of hydrogen peroxide to water and oxygen. FMN and
FAD are considered prosthetic groups by some workers while others consider them
to be coenzymes.
Both coenzyme and prosthetic group take part in group transfer reactions. Prosthetic
group requires a single apoenzyme for picking up the group and transferring the
same. Coenzyme requires two Apo enzymes, one for picking up the group and the
second for transferring the group, e.g., NAD+, NADP+, CoA
. (a) Coenzyme is essential for bringing the substrate in contact with the enzyme,
(b) It picks up a product of the reaction, e.g., hydrogen in case of NAD+
(nicotinamide adenine dinucleotide) or NADP+.
(
8. CLASSIFICATION OF ENZYME
The continuous increase in our knowledge of enzymology needs the proper classification of
These biomolecules for its application. Different approaches have been taken into account
For this classification. Different approaches in this regard as follows:
i. Substrate acted upon enzyme- Duclaux ( 1883) named enzyme by adding suffix –ase
Upon the substrate catalyzed. For carbohydrate, carbohydrases, protein for proteases
And lipase for lipid like this. Maltase for maltose, sucrase for sucrose etc for some
Specific cases.
ii. Type of reaction catalyzed- According to the nature of the reaction catalyzed, suffix –ase
Is added for the same. Hydrolyses for hydrolysis, oxidases for oxidation, dehyrogenases
For dehydrogenation etc.
iii. Substrate acted upon and the type of reaction catalyzed- It can give the clues both for
Substrate utilized and the type of the reaction catalyzed. Succnic dehydrogenase catalyses
Both for the dehydrogenation and Scuccinic acid.
9. iv. Substance that is synthesized- A few enzymes have been named by adding the suffix – ase
To the name of the substance synthesized. Rhodonase that forms rhodonate irreversibly from
Hydrocyanic acid and Sodium thiosulphate .
v. On the basis of the chemical composition of the Enzyme- Based on the chemical compos
-ition, it has been named as follows-
Enzyme molecule being protein only like pepsin, trypsin, Urease, Papain , etc.
Enzyme molecule with protein & cation - Carbonic anhydrase with Zn +2 as cation,
Enzyme molecule with a protein & non-protein organic compound- Iron porphyrin enzymes
Cytochrome C, Flavoprotein enzyme like glycine oxidase, Diphosphothiamin like β-carboxy
lase, Enzymes requiring other coenzymes like amino acid decarboxylase etc.
VI. Overall chemical reaction taken into consideration: According to IUB, precise, descriptive
And informative classification has been offered comprising of two parts in enzyme along with
The additional information regarding the nature of the reaction followed by a distinctive serial
4 digit Numbers to denote the same.
10. i. A recommended name usually short and appropriate for every day use,
ii. A systematic name that identifies the reaction catalyses by it,
iii. A classification number which is used where accurate and unambiguous identification of
Enzyme is required . For example-
The classification number of enzyme , ATP: Creatine Phosphotransferase is EC 2.7.3.2
Where EC= Enzyme Commission,
First number 2 for class name –Transferase,
Second number, 7 for subclass name Phosphotransferase,
Third number , 3 for sub-class name – Phosphotransferase with nitrogen group as acceptor,
Fourth number, 2 for cardinal number of the enzyme within in sub subclass in question.
6 major classes with some examples can have the pleasure of understanding in this regard-
1. Oxidoreductases- It brings about the oxidation and reduction between the two substrates –S
& S′
S (Reduced) + S′ ( Oxidized ) →S ( Oxidized ) + S′ ( Reduced), it may be Oxidases like Cyto
Chrome oxidize or Reductases like Succinate dehydrogenase.
11. Transerfase - Enzyme catalyzed the transfer of a group G , other than Hydrogen between a
Pair of substrate. S & S′ are called transferases.
S-G + S′----- S + S′-G ,
In these are included the enzyme catalyzing the transfer of one-carbon groups, aldehydes or
Ketonic residues, and acyl, glycosyl, alkyl, phosphorous or sulpher containing groups. Some
Important subclasses are Aceyltransaferase. Glycosyltransferases etc.
Acetl-CoA + Choline- CoA + O-Acetylcholine.
Hydrolyses- these catalyses the hydrolysis of their substrates by adding constituents of water
Cross the bond they split. The substrates include ester, glycosyl, ether, peptide, P-N bonds etc.
Different enzymes like Lipase, β- galactosidase are some of the examples.
L- arginine +H2o---- L- ornithine + Urea
Lyases- These are those enzymes that catalyses the removal of groups from substrates by
Mechanisms other than the hydrolysis, leaving double bonds. Form double bonds by the
Elimination of a chemical group or catalyses cleavage by electronic rearrangement.
Carboxylase, Fumarase, PEPcarboxylase, PEPcarboxykinase etc.
12. Isomerases - These catalyze the interconversions of optical, geometric or positional isomers by
Intramolecular rearrangement of atoms or groups. This rearrangement atoms or molecule to
To form a structural isomer is the key aspect of this reaction. Some examples in this regard are
Isomerase, Epimerase, Mutase etc.
L-alanine---------D-alanine in presence of alanine racemase
Ligases or Synthetase- These are the enzymes catalyzing the linking together of two compounds
The energy made available due to simultaneous breaking of a pyrophosphate bond in ATP or
Similar compounds. This category includes enzymes catalyzing reactions forming C-O, C-S
And C-C bonds.
Polymerase is such type of enzymes that link monomers or sub-groups into a polymer such as
RNA or DNA. Glutamine synthetase, Asparagine synthetase, DNA polymerase etc are some of
the Enzymes deserve mentioning in this regard.
In addition to the classification of enzymes, there are different other attributes as far as
Enzyme classification is concerned.
13. PROPERITIES OF ENZYME
c) The product picked up by a coenzyme is transferred to another reactant.
Certain workers use the term cofactor for any loosely bound non-protein group.
The organic cofactor is called coenzyme
Most of the coenzymes are made of water soluble vitamins, В and C, e.g.,
thiamine, riboflavin, nicotinamide, pyridoxine. Inorganic cofactors include ions
of a variety of minerals e.g., calcium, iron, copper, zinc, magnesium,
manganese, potassium, nickel, molybdenum, selenium, cobalt.
They usually function as activators by forming one or more coordination bonds
with both the substrate and active site of enzyme. Fe2+ is cofactor for catalase.
Chloride ion stimulates activity of salivary amylase. Zinc is required for
carboxypeptidase NAD+ and NADP+ activity.
15. PROPERITIES OF ENZYME
1. Catalytic Property-Extraordinary catalytic power; a small amount of enzyme is
enough to convert large quantity of substrate into products, having turnover
number(Number of substrate molecules converted by one enzyme molecule
/Second) 0.5-600000
2.Specificity-Specific in their action which may be
Bond specificity,(Peptide bond)
Group specificity,(specific bond like peptide bond by pepsin as endopeptidase)
Substrate specificity,(absolute specificity acts on a particular substrate)
Cofactor specificity(Specific to cofactor)
Geometric specificity(Act on similar geometric structure)
3.Reversibility-Most of the enzymes catalysed reactions are reversible
4.Temperature sensitive- Increases with the increase of temperature
18. PROPERITIES OF ENZYMES
5. Sensitive to pH-Some enzymes active on low pH(Pepsin Surcease) while other
are high pH(Trypsin, Lipase) but the correct pH is called optimum pH
6.Colloidal nature-High molecular weight with large surface area, hydrophilic in
nature.
7. Inhibition of enzyme activity either by Competitive, Non-competitive &
uncompetitive inhibitors reversibly or irreversibly.
8.Accleration of enzyme activity by ions like Mn, Ni, Cl, Mg etc needed in low
concentration called metal activators-either anti-inhibitors or protectors.
9.Isoenzymes-more than one enzyme form that can act on the same substrate and
convert into the same product having multiple forms.e.g Malate dehydrogenase
10. Regulatory enzymes-Sense various metabolic signals and change their
catalytic rates accordingly
Slowest enzymes- Lysozyme, Fastest enzyme-Carbonic anhydrase
19. ACTIVE SITES
The enzymes have specific catalytic sites known as active sites or active
centres or catalytic sites or substrate sites. The tertiary or quaternary structure
of the enzymatic proteins are produced due to the folding of the polypeptide
chain(tertiary) or chains(quaternary structure) in such a way or ways to create
active site or sites having correct molecular dimensions and appropriate
topology to accommodate and bind with the specific substrate or substrates.
The active centre of the enzymes include cofactors.
The number of the active centres in oligometric enzymes(those possessing a
quaternary structure) may be equal to the number of sub units , i.e. one centre
per unit
The active sites has two parts-contact site for binding a substrate and a
catalytic site at which the conversion of the bound substrate take place
Usually, active centre is made up of 12-16 amino acids residue of a polypeptide
chain but it may be larger.
21. FUNCTIONAL GROUPS OF ENZYME ACTIVE CENTRE
In simple enzymes, the role of the functional groups at the contact and catalytic
side sites is assigned to the side chain radicals of amino acids only. But in
conjugated enzymes, the leading part is the Co-factors.
The following functional enzyme groups take part in catalysis:
COOH groups of dicaboxylic amino acids and terminal group of the
polypeptide chain,
NH2 group of lysine and terminal NH2 groups of polypeptide chain
Guanidine group of arginine.
Indole group of tryptophan.
Imidazole groups of histidine.
OH groups of serine and threonine.
SH groups of cysteine and disulphide group of cysteine.
Thioester group of methionine.
Phenol group of tyrosine.
24. ABSOLUTE VS GROUP SPECIFICITY
We have already learnt that the enzymes are specific in their action. Their specificity
Lies in the fact that they may act- on one specific type of substrate molecule or on a
Group of structurally –related compounds or on only one of the two optical isomers of
a compound or only one of the two geometrical isomers. According to the four
patterns of enzyme specificity, absolute specificity and group specificity is important.
ABSOLUTE SPECIFICITY: Some enzymes are capable of acting on only one
substrate. For example, Carbonic anhydrase brings about the union of carbon-di-oxide
with water to form carbonic acid.
H2O + CO2--------H2CO3 ( enzyme, Carbonic anhydrase)
GROUP SPECIFICITY: Some enzymes are capable of catalyzing the reaction of
Structurally related group of compounds. For example, lactic anhydrase (LDH)
catalyses the interconversions of pyruvic acid or lactic acid and also some other
Structurally related compounds .
CH3 CO.COOH + NADH +H+------ CH3CHOH.COOH
+ NAD+ ( Lactic dehydrogenase)
25. HOW ENZYME WORKS
In course of action, enzyme must temporarily form a chemical bond or enters
into a transient complex with the substrate whose reaction it catalyses. This
specificity of substrate recognition in both formation of the complex and
catalytic chemical transformation is due to the presence of a special domain on
the surface of the enzyme-active sites.
A group of amino acids constitute the active site and their side chains form
weak chemical bonds with substrate.
The nature of the enzyme substrate transformation takes place a paramount
importance & this has been explored by a number of theories-
Lowering the activation energy of substrates by enzymes-the energy barrier
called activation energy -”extra amount of energy which is a free average
molecule must obtain from some source, so that it can require the activated
state to react with the reactants”
27. SOME EXAMPLES
1.Activation energy for acid hydrolysis of sucrose is 26Kcal/mole but in
presence of Invertase, its activation energy is -11.5 Kcal/mol . Thus, the
activation energy is lowered by 37.5 Kcal/mol because of 26-(-11.5)=37.5
kcal/mol.
2.Energy of activation for decomposition of H2O2 is 18.0 Kcal/mol but in the
presence of catalyse, its activation energy is 2.0Kcal/mol . Thus activation
energy is lowered by 16.0 kcal/mol.
3.In the living cell dynamo of energy production, both the phosphorylation and
dephosphorylation , in presence of ATPase, 10 millions of ATP are converted
to ADP or vice versa every second due to presence of enzyme catalysed
biochemical reactions.
30. ENZYME SUBSTRATE FORMATION
Two main theories proposed in this regard-
1. Lock-Key Hypothesis
2.Induced fit hypothesis
3.Multisubstrate Reactions
a. Ordered mechanism
b. Random mechanism
c. Ping pong Mechanism
d. Theorell Mechanism
LOCK & KEY HYPOTHESIS
The specific action of an enzyme with a single substrate can be explained using
a Lock and Key analogy first postulated in 1894 by Emil Fischer. In this
analogy, the lock is the enzyme and the key is the substrate. Only the correctly
sized key (substrate) fits into the key hole (active site) of the lock (enzyme).
32. MODE OF LOCK--KEY THEORY
1.The enzymes temporarily form weak chemical bonds with the substrate.
2. A group of 3 dimensional amino acid residues constitutes the active site and
their side chains form weak chemical bonds with the substrate.
3.The conformation of active site is such that it is exactly complementary to the
substrate and so catalyses just as a key fits only its lock not the others.
4.This theory is supported from the study of competitive inhibition of enzymes
activity. The competitive inhibitors have structural similarity with the substrate
molecules both of which compete for the same active site on the enzyme
molecule. If the active site is rigid and specific for the given substrate ,
reversibility of the reaction would not occur because the structure of the product
is different from that of the substrate and would not fit well.
This model fails to explain the backward reaction and the stabilization of the
transition state the enzyme achieve.
34. INDUCED- FIT HYPOTHESIS
The induced fit model is a model for enzyme-substrate interaction. It describes that
only the proper substrate is capable of inducing the proper alignment of the active
site that will enable the enzyme to perform its catalytic function. The induced fit
model suggested by Daniel Koshland in 1958.
The active site of enzyme can be induced by close approach of the substrate (or
product) to undergo a change in conformation(shape) that allows a better
combination between the two(Enzyme and substrate or product).This is called
induced fit hypothesis and here the E-S complex may be ionic, hydrogen and Van der
waals force. The active site continues to change until the substrate is completely
bound, at which point the final shape and charge distribution is determined.
According to the induced-fit model of enzyme activity, this binding changes the
conformation—or shape—of both the enzyme and the substrate. This brings the
substrate closer to the higher energy transition state needed for the reaction to occur,
for instance, by weakening its bonds so that it can more readily react. Enzymes may
35. CONTINUATION-------
also speed up a reaction by creating conditions within the active site that are more
conducive for the reaction to proceed than the surrounding cellular environment.
Once the products of the reaction are formed, they are released from the active site
and the enzyme can be used to catalyze reactions once again.
An illustration of the competitive inhibitors or substrate analog may also be given.
On contact with the true substrate, all groups are brought into correct spatial
orientation. But attachment of a competitive inhibitor, which is either too “slim” or
too “bulky” induces incorrect alignment.
As to the sequence of events during conformational changes, 3 possibilities exist.
a. The enzyme may first undergo a conformational changes, then bind substrate.
b. An alternative pathway is that the substrate may first be bound and then
conformational changes may occur.
c. Both the processes may occur simultaneously with further isomerisation to the final
conformation.
38. CONTINUATION----------
Leonor Michaelis & Maud L. Menten (1913), while studying the hydrolysis of
sucrose by the enzyme, invertase, proposed the theory based on the following
assumptions:
Only a single substrate & single product is involved,
The process proceeds essentially to completion,
The concentration of the substrate is much greater than that of the enzyme of
the system,
An intermediate ,Enzyme- Substrate complex is formed,
The rate of decomposition of the substrate i.e proportional to the concentration
of the enzyme substrate complex.
The theory postulates that the enzyme(E) forms a weakly-bonded complex(ES)
with the substrate (S). this Enzyme -Substrate complex, on hydrolysed,
decomposes to yield the reaction product(P) and the free enzyme(E). The
reaction can be symbolically represented: E+S→ES→E+P(Reversible)
40. ENZYME INHIBITION & FACTORS AFFECT ON ENZYME
INHIBITION
The interaction between the substrate and the enzyme takes place in a
particular region of the enzyme molecule called the active site.
In many instances compounds other than the normal substrate for a particular
enzyme-catalyzed reaction may bind to the enzyme’s active site, and this has
a significant effect on the kinetics of the normal reaction.
One possible consequence of this phenomenon is the inhibition of normal
enzyme activity, and such compounds are therefore called enzyme inhibitors.
(Usually, the inhibitor is unaltered by its interaction with the enzyme.) In
some instances, the normal substrate (S) and the inhibitor (T) compete with
each other for the active site of the enzyme; the manner in which this affects
the normal kinetics of the reaction. Vmax is not altered by the presence of a
competitive inhibitor, but the KM is elevated.
41. ENZYME INHIBITION-TYPES
Enzyme inhibition is the decreases in the rate of enzyme-catalysed reaction mediated
by the inhibitors. The inhibitors usually try to prevent the normal binding of enzyme
with the substrate, thus declining the rate of enzyme catalytic pathways. As per as
mode of execution, he inhibitors are of broadly two types-i. Irreversible Inhibition-
Occur by Irreversible inhibitors which combine or destroy a functional group of the
active site required for enzyme activity. Di-isopropyl fluro phosphate(DFP), Cyanide,
Penicillin, aspirin are some inhibitors act as irreversible inhibitions.
ii. Reversible inhibition-Do not impart any permanent damage of the active site of the
functional groups of the enzyme molecule. If the inhibitors are withdrawn from the
system, enzymatic activities resume to be normal pathways.
It may be three types-
a. Competitive Inhibition
b. Non-competitive inhibition
c. Uncompetitive inhibition.
42. COMPETITIVE INHIBITION
A classic example of this form of
inhibition is the competition between
succinic acid and malonic acid for the
enzyme succinic acid dehydrogenase.
In this instance, competition between
these two compounds for the active
site of the enzyme is understandable
in view of their marked chemical
similarity (Fig. 8-9). Succinic acid is
the normal substrate for the enzyme
and, in the absence of the inhibitor, is
converted to fumaric acid.
(a) Chemical Function of a succinic
acid and malonic acid (b) Malonic
acid is a competitive inhibitor of
succinic acid dehydrogenase.
43. NON-COMPETIVE INHIBITION
Enzyme inhibition can also be
noncompetitive in that the binding of
the inhibitor to the enzyme cannot be
reversed by increasing the
concentration of the normal substrate.
A common example of negative
inhibition is the action of heavy
metals such as mercury on the active
sites of enzymes containing a reactive
Sulf-hydryl (i.e., -SH) group. In
effect, the presence of the inhibitor
prevents some percentage of the
enzyme present from participating in
normal catalysis. As a result, the
maximum reaction velocity is
depressed, even though the Ku value
remains the same (Fig. 8- 10).
44. UNCOMPETITIVE INHIBITION
This form of inhibition occur when the
inhibitor binds reversibly only with ES
complex to form ESI ( Enzyme-
Substrate- Inhibitor) complex . ESI is
unable to be converted to any product.
These type of inhibitors are most
effective at high concentration. It
inhibits enzyme catalysis. This type of
inhibition is of rare occurrence with
single substrate and often found in
reductions with 2 or more substrates.
Uncompetitive inhibition is not reversed
by increasing the substrate
concentration . Thus, it is the most
important one where the slope remains
constant but Km value will vary.
45. FACTORS AFFECTING ENZYME ACTIVITY
Different factors play a very important role as far as the enzyme activity is concerned.
The following factors can be addressed in this regard:
i. Substrate Concentration- The rate of enzymatic reaction is enhanced with the increase
of the substrate concentration but up to a certain point, the rate of the enzymatic
action does not change with the further increase of the substrate concentration. This
Point is called Vmax , the maximum velocity where the enzyme is fully saturated with
the substrate. The saturation effect is mostly visible in all cases. In some cases, the
Enzyme activity may decrease at higher substrate concentration called substrate inhibition.
2. Temperature- Enzymes are very sensitive to temperature –thermo labile being protein in
nature. With the increase of temperature, enzyme activity increases and it is maximum at
an optimum temperature ( about 40℃) but with the subsequent increase of temperature
the rate of the enzyme activity decreases and at a maximum temperature, it becomes zero.
The factor by which the velocity increases for a rise of 10 ℃ , called Q10 or temperature
Coefficient value. Both for the increase of 10℃ and decrease of 10℃, both the cases,
Q10 becomes 2. In rare cases, beyond 50-60℃, enzymes become operational except
Taq DNA polymerase.
46. 3.pH- Not only the temperature, enzymes are extremely sensitive to change in pH. Most of
the enzymes becomes functional within a range of 4-10.Very few enzymes becomes
functional above or below this value. Above or below the optimum pH value, the activity
of the enzyme decreases. The optimum pH of an enzyme depends upon the proton donating
groups of the active site of the enzyme. Extreme pH changes lead to enzyme denaturation
that may involve alterations in protein structure and binding of prosthetic group or other
Cofactors leading to their denaturation. Each enzyme have optimum pH like peroxidase has
pH optimum at 6.8
4. Inhibitors- Inhibitors are those substances which decrease the rate of enzyme catalyzed
reactions by combining with the enzyme and preventing the normal binding of enzyme and
Substrate molecule. The inhibitors may be normal or synthetic compounds or the products
Of the reaction itself. Anti-metabolites are the group of the same. Inhibitors may be
reversible or irreversible.
5. Redox Potential- Redox potential of the cell influences the enzyme activity. Oxidizing &
reducing enzymes alter the red ox potential of the cell. As a consequences, the enzymes are
Influenced. The enzyme having readily oxidisable Sulf-hydryl ( -SH) group in their active
Site may bear this property.
47. 6. Other forms- Enzyme activity may be activated by some ions especially cations
present around the active site like Ca+2, K+, Zn +2, Mn+2 etc. In some cases, they are
loosely bound with the enzymes and act as cofactors. In some other cases, not being a part
of the enzyme, in the enzymatic process by modifying either the substrate or the enzyme
molecules. Enzyme activity may also be activated by the anions like Cl- that enhances the
activity of the enzyme, salivary amylase.
MULTIENZYME SYSTEMS
A few examples of complex enzyme systems are known to exist. These are not independent
molecules but occur as aggregates in a mosaic pattern involving several different enzymes.
Pyruvic acid dehydrogenase of E.coli is one such example. The complex molecule has a
Molecular weight 4,800, 000 and consists of three enzymes: 24 molecules Pyruvate
decarboxylase, 24 moles of dihydrolipoic dehydrogenase and 8 subunits of lipoyl reductase
Transaceytylase . Each component of this enzyme complex is so arranged as to provide an
efficient coupling of the individual reactions catalyzed by these enzymes. In other words ,
the product of the first enzyme becomes the substrate of the second and so on.
48. BIOLOGICAL ROLES OF ENZYMES
Enzymes play a very important role in the applications of our daily life and the manifold
Applications of the enzymes are stated below:
i. Wine manufacturing- Enzymology has an opened a horizon in the wine industry like
papain is used in brewing industry as a stabilizer for chill-proof beer. It removes small
amounts of protein that causes the turbidity of the chilled beer.
ii. Cheese making- Since long the animal rennin is employed in making cheese. The enzyme
Rennet is obtained on a commercial scale from the fourth or the true stomach in
unweaned calves.
iii. Candy making- Invertase helps in preventing granulation of sugars in soft-centered candy.
Another enzyme, lactase prevents formation of lactose crystals in ice cream which would
otherwise not allowed the product seem sandy in texture.
iv. Bread whitening- Lipoxygenase is used for whitening the breads.
v. Tenderizing the meat- Hydroxyprolyl residues create bonds in collagen helices which
Contribute the tough and rubbery texture often associated with cooked meat. Protease prior
to cooking can help to overcome the issue.
49. VI .Correcting digestion-When the enzyme are present insufficiently in the body,
digestive disorders are issues. These may be corrected by supplying enzymes and Pepsin,
Papain, amylases like enzymes are helpful in this regard.
vii. Wound healing- Proteolytic enzymes from pig pancreas are used to alleviate skin
diseases like bed sores and sloughing wounds. These enzymes act by destroying proteolytic
enzymes of man, that prevent the healing of such wounds.
viii. Dissolving blood clot- The enzyme, urokinase is manufactured from urine is being
effectively used in the treatment of the blood clot in brain, artery and other circulatory
Diseases. The enzyme , Streptokinase id extensively used in preventing heart attacks as
clots are responsible for fatality in 9 out of 10 cases.
ix. Diagnosing hypertension- It is a kind of radioimmunoassay for diagnosing hypertension
by the activity of rennin which is indirectly calculates the angiotensin-I formed by the
action of rennin.
x. In addition to these, Breaking down the chemicals, destroying acids , amylyzing
bio-chemicals , syrup manufacturing like other products, enzymes are used extensively.
50. References:
1. Google for images,
2. Different open sources of information of WebPages
3. Biochemistry- Lehninger
2. Biomolecules & Cell Biology- Arun chandra Sahu,
3. A textbook of Botany (Vol. II) Ghosh, Bhattacharya, Hait
4. Fundamentals of Biochemistry- Jain, Jain, & Jain,
5.A Textbook of Genetics- Ajoy Paul
DISCLAIMER:
This presentation has been made to enrich open source of learning without any
financial interest. The presenter acknowledges Google for images and other
open sources of information to develop this PPT.