2. • Give name of co-enzyme and its one biological functions of the
• following vitamins :
• (i) Thiamine hydrochloride
• (ii) Pyridoxin
• (iii) Riboflavin
• (iv) Nicotinamide
• Explain the following terms :
• (i) Adoptive enzymes
• (ii) Constitutive enzymes
• (iii) Isoenzymes
• (iv) Allosteric enzymes
• Explain four pharmaceutical and therapeutic uses of enzymes.
• Enzymes
• (ii) One unit of enzyme activity
• (iii) Turnover number of enzymes
• (iv) Specific activity of enzymes
• What is enzyme inhibition ? Give six points of difference between
• competitive inhibition of non-competitive inhibition.
• Enlist factors affecting rate of enzyme catalysed reaction. Explain in
• detail effect of substrate concentration with the help and curves and
• equations.
• What are co-enzymes ? Name co-enzymes derived from :
• (i) Vitamin B1
• (ii) Vitamin B3
3. Explain enzyme binding of a substrate with the help of suitable models.
Enlist various factors affecting rate of enzyme catalysed reaction. Explain in
detail role of temperature.
(i) Exoenzymes
(ii) Endoenzymes
(iii) Induced enzymes
(iv) Zymogens
What are enzyme ? How they are classified on the basis of type of reactions
catalysed by them ? Give diagnostic & therapeutic applications of enzyme.
4. • Mention the factors affecting rate of enzyme catalysed reactions. Explain effect of tem
• Define enzyme & classify them with example. perature and pH on enzyme catalysed reaction.
• What is an active site of an enzyme? Explain ‘lock and key model’ and ‘Induce Fit Model’.
• Enumerate the factors that affect the rate of enzyme catalysed
• reaction. Describe the effect of temperature and pH.
• What is meant by ‘marker enzymes’?
• What is enzyme inhibition? Explain competitive inhibition with example.
• Enlist factors affecting rate of enzyme catalysed reaction. Explain effect of temperature.
5. Enzymes (Biocatalysts)
Definition: substance that increase rate of chemical reaction without
itself undergoing any change in the overall process.
Properties:
• Enzymes are proteinous in nature
• They increase the rate of reaction by lowering the energy of
activation
• They catalyze nearly all the chemical reactions taking place in the
cells of the body
• Enzymes have unique three-dimensional shapes that fit the shapes
of reactants (substrates), essential for enzyme activity
• The functional unit of enz. Is known as holoenzyme (active
enzyme) = apoenzyme (protein part)+coenzyme (non-protein part)
7. Naming Enzymes
• The name of an enzyme identifies the reacting substance
- usually ends in –ase
• For example, sucrase catalyzes the hydrolysis of sucrose
• The name also describes the function of the enzyme
• For example, oxidases catalyze oxidation reactions
• Sometimes common names are used, particularly for the
digestion enzymes such as pepsin and trypsin
• Some names describe both the substrate and the function
• For example, alcohol dehydrogenase oxides ethanol
8. Class Reaction Enzyme
Oxidoreductase Oxidation-reduction Cytochrome oxidase
L & D amino acid oxidase
Transferases Transfer of
functional group
Transaminase
Phosphorylase
Hydrolases Hydrolysis Lipase, pepsin, urease
Lyases Add /remove of
water ,ammonia,
CO2
Aldolase, Fumarase,
Histidase
Isomerases Isomerization
reaction
Retinol Isomerase
Phosphohexose isomerase
Ligase Synthetic reaction Glutamine synthetase
succinate thiokinase
11. Active Site of an Enzyme
• The active site is a region within an
enzyme that fits the shape of
substrate molecules
• Active site made up of amino acid
• Active site regarded as pocket or
cleft
• Not rigid in shape
• Substrate binding site & catalytical
site
• Substrate bind at the active site by
weak non-covalent bonds
• Enzyme are specific in function
• E+S ES P + E
12. Enzyme Catalyzed Reactions
• When a substrate (S) fits properly in an active site, an
enzyme-substrate (ES) complex is formed:
E + S ES
• Within the active site of the ES complex, the reaction
occurs to convert substrate to product (P):
ES E + P
• The products are then released, allowing another substrate
molecule to bind the enzyme
- this cycle can be repeated millions (or even more) times
per minute
• The overall reaction for the conversion of substrate to
product can be written as follows:
E + S ES E + P
13. Example of an Enzyme Catalyzed Reaction
• The reaction for the sucrase catalyzed hydrolysis of sucrose to
glucose and fructose can be written as follows:
E + S ES E + P1 + P2
where E = sucrase, S = sucrose, P1 = glucose and P2 = fructose
15. Lock-and-Key Model (Fischers template theory)
• In the lock-and-key model of enzyme action:
- the active site has a rigid shape
- only substrates with the matching shape can fit
- the substrate is a key that fits the lock of the active site
• This is an older model, however, and does not work for all
enzymes
16. Induced Fit Model (Koshland’s Model)
• In the induced-fit model of enzyme action:
- the active site is flexible, not rigid
- the shapes of the enzyme, active site, and substrate adjust to
maximumize the fit, which improves catalysis
- there is a greater range of substrate specificity
• This model is more consistent with a wider range of enzymes
17. Enzyme Specificity
• Enzyme are highly specific in their action
• Stereospecificity or Optical Specificity
• Reaction Specificity
• Substrate Specificity
18. Stereospecificity or Optical Specificity:
Eg. Glucokinase on D-Glucose
L- amino acid oxidase on L-amino acid
D- amino acid oxidase on D-amino acid
Reaction Specificity
Eg. Amino acid undergoes different reaction – transamination,
deamination, decarboxylation
Substarte Specificity
i) Absolute- eg.Glucokinase on glucose, urease on urea
ii) Relative- eg. Trypsin hydrolyse peptide linkage in arginine or
lysine
iii) Broad- eg. Hexokinase act on glucose, fructose, mannose and
glucosamine
19. Enzyme Inhibition
• Substance which binds with enzyme & brings about a
decrease in catalytic activity of that enzyme.
• Two broad categories
• Reversible inhibition
i) Competitive
ii) Non competitive
• Irreversible inhibition
20. Reversible Enzyme Inhibition
A reversible inhibitor is one that will cause a temporary loss of
enzymatic activity. This substance forms a non-covalent interaction
with the enzyme
. Reversible inhibitors can be
Competitive inhibitor-is any compound that bears a structural
resemblance to a particular substrate and thus competes with
that substrate for binding at the active site of an enzyme
The inhibitor is not acted on by the enzyme but does prevent
the substrate from approaching the active site.
Non-competitive inhibitor- A noncompetitive inhibitor attaches
at an allosteric site, which is any site on the enzyme that is not
the active site. The attachment of the non-competitive inhibitor to
the allosteric site results in a shift in three-dimensional structure
that alters the shape of the active site so that the substrate will no
longer fit in the active site properly
24. Factors affecting enzyme activity
• Concentration of enzyme
• Concentration of substrate
• Effect of Temperature
• Effect of pH (Hydrogen Ion Conc.)
• Effect of activators
• Effect of product conc.
• Effect of light and radiation
• Effect of time
25. Concentration of enzyme
Assuming a sufficient
concentration of substrate is
available, increasing enzyme
concentration will increase the
enzyme reaction rate.
26. Concentration of Substrate
• At a constant enzyme
concentration and at lower
concentrations of substrates, the
substrate concentration is the
limiting factor.
• As the substrate concentration
increases, the enzyme reaction
rate increases.
• At very high substrate
concentrations, the enzymes
become saturated with substrate
and a higher concentration of
substrate does not increase the
reaction rate.
27. Effect of Temp.
• Each enzyme has an optimum
temperature at which it works best.
• A higher temperature generally
results in an increase in enzyme
activity.
• As the temperature increases,
molecular motion increases
resulting in more molecular
collisions.
If, however, the temperature rises above a certain point, the heat will
denature the enzyme, causing it to lose its three-dimensional
functional shape by denaturing its hydrogen bonds. Cold
temperature, on the other hand, slows down enzyme activity by
decreasing molecular motion.
28. Effect of pH
• Each enzyme has an optimal
pH that helps maintain its
three-dimensional shape.
• Changes in pH may denature
enzymes by altering the
enzyme's charge.
• This alters the ionic bonds of
the enzyme that contribute to
its functional shape.
29. Effect of activators
For optimal activity, several enzymes require
inorganic metallic cations such as Mn2+, Mg2+,
Zn2+, Co2+, Ca2+, Cu2+, K+, Na+, and others.
Anions are occasionally needed for enzyme
function, such as a chloride ion (CI–) for
amylase.
30. Application of Enzyme
Clinical Application:
• Trypsin: Acute thrombophlebitis (Blood clot & inflammation in
vein)
• Streptokinase: Fibrinolysis and dissolution of clot
• Pepsin: Gastric achylia (Undeveloped gastric gland)
• Urokinase: Pulmonary embolism and myocardial infraction
31.
32. • Asparginase: Leukemia
• Lysoenzymes : Eyes infection
• Galactosidase useful in treatment of
lactose intolerance.
33. Medicinal application:
• Sulphonamide - Antibacterial
• Allopurinol – Treat Gout
• Xanthin/ Hypoxanthin Xanthin oxidase Uric acid
Diagnostic Application
The enzyme whose presence or decrease or increase in level of blood,
CSF or urine indicates the presence of disease or disorder is known as
marker enzymes
1) Glutamate oxaloacetate transaminase in Myocardial infraction
2) Glutamate pyruvate transaminase in Hepatitis
3) Creatinin kinase in cardia infection
4) Lipase – Actute pancretitis
5) LDH- Infraction , Leukemia, carcinoma
34. Pharmaceutical Application:
• Penicilline acylase for Antibiotics production
• Papain enzyme used in production of protein hydrolysate
• Rennin is used for cheese preparation
• Glucose isomerase is used for production of syrup
• Alpha amylase is used in food industry to covert starch to
glucose
• Papain, pepsin and trypsin are used in preparation of digestants
35. Exoenzymes / Extracellular enzymes:
Secreted outside the cell
E.g..: proteoses, lipases.
Endoenzymes / Intracellular enzymes:
Present inside the cell
E.g..: synthetases, phosphorylases
Constitutive Enzymes:
Produced in absence of substrate. Constitutive enzymes are produced
in constant amounts without regard to the physiological demand or
the concentration of the substrate
Eg.: Enzymes of glycolytic series.
Induced Enzymes:
Produced in presence of substrate.
Eg.: hepatic microsomal enzymes.
36. • Zymogens/ Proenzyme
Produced naturally in an inactive form which can be activated
when required.
eg. Prothrombin – Thrombin, Pepsinogen- pepsin
• Isoenzyme:
Isoenzymes are different forms of an enzyme that catalyze the same
reaction in different tissues in the body
Eg.lactate dehydrogenase
• Coenzyme:
Nonprotein, organic substance required for some enzyme function
or activity of enzyme
