4. DISCOVERY OF ENZYME
• French chemist Anselme Payen was the first to discover an
enzyme, Discovered diastase and cellulose , in 1833.
• 1878: German physiologist Wilhelm Kuhne first used the term
enzyme, which literally means “in yeast"
5. DEFINATION
• Enzymes are biocatalyst that speeds up digestion and
metabolism.They are located in the cells, cytoplasm, mitochondria,
tissues and body fluids.
• Endoenzymes :- that function within the cells. Most of the enzymes
are these types. E.g. metabolic enzymes (cytochrome oxidase)
• Exoenzymes :- that are liberated by cells and catalyse reactions
outside the cell. E.g. digestive enzymes (amylase, lipase, protease)
6. STRUCTURE OF ENZYME
• Enzymes are a linear chain of amino acids, which give rise
to a three-dimensional structure. The sequence of amino
acids specifies the structure, which in turn identifies the
catalytic activity of the enzyme. Upon heating, the
enzyme's structure denatures, resulting in a loss of enzyme
activity, which typically is associated with temperature.
7.
8. PROPERTIES
• Enzymes are biocatalyst of protein in nature, which accelerate the
rate of biochemical reactions but do not affect the nature of final
product like catalyst the enzymes regulate the speed and specificity
of reaction without being used up but unlike catalyst enzymes are
produced by living cells only.
• They are colloidal in nature and may contain a non-protein moiety
(co-enzyme or prosthetic group).
9. *Holoenzyme = Apo-enzyme + Coenzyme
(Protein part) (Non-protein part).
》CO-ENZYMES -Coenzymes are thermostable, dialyzable, low mol
weight non protein organic substances required for the activity .
Coenzymes are also called cosubstrates (synonymous) of the enzymes.
Examples: NAD+, FAD, FMN, TPP, etc.
10. 》Transferring coenzymes = Some group transferring coenzymes are:Thiamine
pyrophosphate (TPP)
• Coenzyme A (COA-SH), Pyridoxal phosphate (B6-PO4) etc.
》Hydrogen transferring coenzymes - Nicotinamide adenine dinucleotide (NAD+) and
Nicotinamide adenine dinucleotide phosphate (NADP+)
Flavine adenine dinucleotide (FAD) Flavine mononucleotide (FMN) etc.
• CO-FACTORS = Activity of many enzymes depends on the presence of certain metal
ions which are called as cofactors.
• e.g. Mg++,Mn++,Fe++, K+, Zn++, Ca++, Cu++, etc.
11. NOMENCLATURE:-
• In most cases, enzyme names end in -ase
● The common name for a hydrolase is derived from the substrate.
》Urea: remove -a, replace with -ase = urease
》Lactose: remove-ose, replace with -ase = lactase
● Other enzymes are named for the substrate and the reaction
catalyzed
》Lactate dehydrogenase
》 Pyruvate decarboxylase
12. EC NUMBER
• EC numbers are four digits, for example a.b.c.d, where "a" is the class, "b" is the
subclass, "c" is the sub-subclass, and "d" is the sub-sub-subclass. The "b" and "c"
digits describe the reaction, while the "d" digit is used to distinguish between
different enzymes of the same function based on the actual substrate in the
reaction.
• > Example: for Alcohol:NAD'oxidoreductase EC number is 1.1.1.1
• Enzyme Code (E.C.) = Four Digits1. First (main class)= Type of Reaction2.Second
(subclass) = Type of Group involved3. Third (sub-subclass) = denotesSubstrate 4.
Fourth = Individual enzyme name & serial number
13. CLASSIFICATION
• ACCORDING TO THE INTERNATIONAL UNION OF
BIOCHEMISTS (IUB), ENZYMES ARE DIVIDED INTO SIX
FUNCTIONAL CLASSES AND ARE CLASSIFIED BASED ON
THE TYPE OF REACTION IN WHICH THEY ARE USED TO
CATALYSE
14. DIFFERENT CLASSES OF ENZYMES
• 1. Oxidoreductases - transfer electrons(redox reaction)
• 2. Transferases - transfer functional groups between molecules
• 3. Hydrolases - break bonds by adding water
• 4. lyases - elimination reactions to form double bonds
• 5. Isomerases - intramolecular rearrangements
• 6.Ligases - join molecules with new bonds
15.
16. MECHANISM OF ENZYME ACTION
● According to Michaelis and Menten hypothesis, the enzyme
molecule (E) first combines with a substrate molecule (S) to form
an enzyme-substrate complex (ES complex) which further
dissociates to form product (P) and enzyme (E) back.
● E+S - ES Complex → P+ E
● The interaction is between the active sites of the enzyme
molecule and the substrate molecule. It should be understood
that only if the ES complex is formed one can get the products.
17. • Enzyme Substrate Complex (ES):- ES-intermediate non-
stable aggregates, formed after entering substrate to active
site of enzyme, later ES transformed to products and Enzymes
recycled.
●Active site :- active site is region of an enzyme where
substrate molecules bind and undergo a chemical reaction.
The active site consists of amino acid residues that form
temporary bonds with the substrate (binding site) and
residues that catalyse a reaction of that substrate (catalytic
site).
18.
19. FISHER'S LOCK-KEY OR TEMPLATE MODEL OF ES COMPLEX FORMATION.
Emil Fisher proposed that active site provides a rigid, preshaped template which
fits with the size and shape of the substrate molecule. Substrate fits into the
active site of the enzyme as the key fits into a particular lock, hence, called as
Lock and Key model.
Steps:
1. Recognize substrate
2. Enzyme change shape
3. Enzyme bind with substrate, formed ES
4. ES transformed to products
5. Products released, enzyme recycled
20. KOSHLAND'S 'INDUCED FIT" MODEL
• Koshland modified Fisher's concept. The important feature of this model is
the flexibility of the region of active site. According to him, the active site is
not a rigid, preformed template. The substrate during its binding induces
conformational changes in the active site of enzyme, so that the substrate
can bind to the enzyme.
• Steps:
1. Enzyme recognize substrate
2. Enzyme bind with substrate
3. Enzyme change shape
4. Formed ESn-complexes
5. ESn-transformed to products
6. Products released and enzyme recycled
21.
22. FACTORS AFFECTING ENZYME ACTION
Activity of enzymes is markedly affected by certain factors.
》Four important factors are:-
• Temperature
• PH Concentration of enzyme
• Concentration of substrate
• Presence of enzyme Concentration
23.
24. THE ENZYME SHOWS MAXIMUM ACTIVITY AT THE
》OPTIMUM TEMPERATURE :- WHICH IS 40°C TO 50°C FOR
ANIMAL ENZYMES,
60°C IN CASE OF PLANT ENZYMES.
》OPTIMUM PH :- WHICH IS USUALLY IN THE REGION OF 3
TO 9.
25. IMPORTANCE
• Enzymes are critical for every aspect of cellular life enzymes
• Cell shape and motility
• Surface receptor
• Cell cycle
• Metabolism
• Transcription
• Hormone release
• Protien synthesis
26.
27.
28. BIOLOGICAL FUNCTIONS OF ENZYMES
• Enzymes play a important role in the digestive activity of the
enzymes.
• Digestion is the process of turning the food we eat into energy. For example,
there are enzymes in our saliva, pancreas, intestines and stomach. They break
down fats, proteins and carbohydrates
29.
30. 1. The general mechanism is that an
enzyme acts by:
Questions
1.Reducing the activation energy
2.Increasing activation energy
3.Decreasing pH value
4.Increasing the pH value
31. 2. An enzyme that joins the ends of two
strands of nucleic acid is:
1.Polymerase
2.ligase
3.synthetase
4.Helicase
32. 3.Which of the following is produced with
the combination of apoenzyme and
coenzyme:
1.Holoenzyme
2.Enzyme substrate complex
3.Prosthetic group
4.Enzyme product complex
34. 5.The enzyme which hydrolyses starch to
maltose is:
1.Protease
2.Amylase
3.Lactase
4.Maltase
35. 6.This enzyme was first isolated and
purified in the form of crystals:
1.Urease
2.pepsin
3.Amylase
4.Ribonuclease
36. 7.Koshland proposed which model:
1.Fluid mosaic model
2.Induced fit model
3.Lock and key model
4.Reflective index model
37. 8.In the human body optimum
temperature for enzymatic activities is:
1.37-degree celsius
2.25-degree celsius
3.20-degree celsius
4.15-degree celsius
38. 9.Which of the following is the non-protein
component of the enzyme?
1.Cofactor
2.Activator
3.Coenzyme
4.All of these
