Isoenzymes

1. ISOENZYMES
-Keshava Pavan K

2. •Multiple forms of same enzyme catalysing
the same reaction
•Differ in physico-chemical properties

3. •Amino acid composition
–Electrophoretic separation
•Heat stability
–Placental and intestinal isoenzymes of the 6
isoenzymes of alkaline phosphatase are heat
stable
•Susceptibility to inhibitors
–Acid phosphatase-6 isoenzymes
–Prostate portion is tartarate labile
–Bone portion is urea labile

4. •Enzyme kinetics
–K
m and V
max differ
•Immunological properties
–Eg,. CKMB estimation
•Different coenzymes
–Isocitrate dehydrogenase
–Mitochondria- NADH
–Cytoplasm- NADPH

5. •Synthesized from different genes
–Eg,. Salivary and pancreatic amylase are each
formed from different genes
•Oligomeric enzymes
–Lactate dehydrogenase ( polypeptide chains)
–Creatine kinase (4 polypeptide chains)
•Glycoproteins : different amount of
carbohydrate
–Eg,. Alkaline phosphatase – sialic acid ( N Acetyl
neuraminic acid)

6. •Produced from same locus of gene in
different persons
–G6P dehydrogenase has 400 types.