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1. M.Prasad Naidu
MSc Medical Biochemistry, Ph.D,.

2. Based on the type of reaction enzymes can be
classified into SIX MAJORTYPES
Classification of enzymes
1. Oxidoreductases- lactate dehydrogenase
2. Transferases- glucokinase
3. Hydrolases- chymotrypsin, G6Pase
4. Lyases- fumarase
5. Isomerases- phosphoglucoisomerase
6. Ligases- Acyl CoA synthetase

3. Transfer of electrons (Hydride ions or H atoms)
1) Dehydrogenases
2) Oxidases
3) Oxygenases
There are several subclasses
OXIDOREDUCTASE

4. alcohol
aldehyde
Oxidation of Ethanol by Alcohol Dehydrogenase
Remove electrons and/or hydrogen atoms
Dehydrogenases

5. Catalyze incorporation of oxygen
into a substrate
Hydroxylation of Progesterone by a
Monooxygenase
Oxygenases

6. Transfer functional groups in group transfer reactions
1) Amino transferases
2) Kinases
3) Glycosyl transferases
Types of transferases
TRANSFERASES

7. Transfer an amino group from one amino acid to a new keto acid
AminoTransferases (orTransaminase)

8. Catalyze transfer of the
phosphoryl group
Kinases

9. Transfer an activated
glycosyl residue to a
glycogen primer. This is a
key enzyme in glycogen
synthesis
GlycosylTransferases

10. Hydrolysis reactions
The generalized reaction involves hydrolytic cleavage of C-O, C-N,
O-P, and C-S bonds
HYDROLASES

11. R1 C NH
O
R2 R1 C O
-
O
NH3 R2+ H2O +
Cleavage of a peptide bond by peptidases
Peptidase

12. Addition or removal of elements of water, ammonia, or carbon
dioxide
LYASES

13. Removal of an element of CO2 from and -keto acids or amino
acids
R C C
O
O
-
R C H
O
CO2+ H
+
+
O
Decarboxylases

14. The substrates bicarbonate and pyruvate are ligated to form a four-
carbon (C4) oxaloacetate
Pyruvate Decarboxylase

15. Fumarase reversibly converts fumarate to malate. It removes H2O in a
dehydration reaction converting malate to fumarate
Dehydratases

16. Transfer of groups within molecules to yield
isomeric form
Isomerases

17. Isomerases that catalyze inversion at asymmetric carbon atoms
Epimerases

18. Involved in synthetic reactions where two molecules are joined at the
expense of a high-energy phosphate bond of ATP
LIGASES

20. Biotin
Acetyl CoA + CO2 MalonylCoA
ATP ADP + Pi
Enzyme is Acetyl CoA carboxylase or AcetylCoA-CO2
ligase (systematic) code number EC.6.4.1.2ese
enzymes link two substrates together, usually.

21.  km indicates the affinity of enzyme to the
substrate
 Smaller the km larger the affinity
 Larger the km smaller the affinity

22. Substrate conc affects reaction velocity (rate)
 As substrate concentration is increased, Initial velocity
vi, increases until it reaches maximum Vmax.
 further increase in substrate concentration does not
increase velocity the enzyme is said to be saturated.
 Note that the shape of the graphic curve relating to
catalytic activity and substrate concentration is hyperbolic

24. Michaelis – menten equation illustrates in mathematical
terms the relationship between initial reaction velocity , vi, and
substrate concentration.
Km = Michaelis constant
Vmax = maximal velocity
Vi = initial velocity
[s] = substrate concentration
Vmax [s]
Vi =
Km + [s]

25. Km value or Michaelis – menten constant is defined as
substrate concentration (expressed in moles / liter)
to produce half maximal velocity in an enzyme catalysed
reaction at a particular enzyme concentration.
 It indicates that 50% of enzyme molecules are bound
with the substrate molecules.
 It’s a characteristic of an enzyme or signature of an
enzyme.
 Lower the Km value Higher the affinity of the enzyme for
substrate.
 Higher the Km value, the affinity of the enzyme for the
substrate is low.

26. Hexokinase
Glucose Glucose-6-Phosphate
ATP ADP
Glucokinase
HK Km value 10-2 mmol / L
GK Km value 20 mmol / L

27. 1.Hepatic diseases
1.Alanine amino transferase (ALT)
Marked increase in parenchymal liver disease
2. Alkaline phsophatase (ALP)
Marked increase in obstructive liver disease
3.Nucleotide phsophatase (NTP)
Elevated in liver dysfunction with cholestasis
4. Gamma glutamyl transferase (GGT)
Increase in obstructive and alcoholic liver disease

28. II.Myocardial Infarction:
1.Cratine Kinase (CK – MB)
First enzyme to rise following infarction,CK-MB isoenzyme
is specific.
2.Aspartate amino transferase (AST)
Rises after the rise in CK and returns to normal in 4-5 days
3.Lactate dehydrogenase (LDH)
Last enzyme to rise. LDH-1 becomes more than 2 (Flipped
pattern)

29. Enzyme pattern in Myocardial infraction
AST

30. Normal pattern of LDH in serum

31. Flipped pattern of LDH in MI

32. III.Muscle disease
1.Creatine Kinase (CK-MM)
Marked increase in muscle disease. CK-MM fraction is elevated
2. Aspartate amino transferase (AST)
Shows an increase in different types of muscle diseas; not specific
3. Aldolase
Earliest enzyme to rise. But not specific

33. IV. Bone diseases
1.Alkanine phosphatase (ALP)
Marked elevationin osteoblastic bone activity as in rickets. Heat labile bone
isoenzyme is elevated. Also in Paget’s disease.
V.Prostate cancer
1.Prostate specific antigen (PSA)
Marker for prostate cancer. Mild increase in benign prostate enlargement.
2. Acid phosphatase (ACP)
Marker for prostate cancer . Metastatic bone disease especially from a primary from
prostate.