Isoenzymes are multiple forms of enzymes that have the same catalytic activity but differ in electrophoretic mobility and inhibitor responsiveness. They are produced by the same gene undergoing different post-translational modifications in different organs. Two important isoenzymes are lactate dehydrogenase (LDH) and creatine phosphokinase (CPK). LDH has 5 isoenzymes that increase in levels for different diseases like myocardial infarction, viral hepatitis, and leukemia. CPK has 3 isoenzymes where CPK BB increases in brain tumors, CPK MB in heart disease, and CPK MM in skeletal muscle disease. Isoenzymes are medically important for disease diagnosis and indication of affected organs
2. Definition
Can told to this enzymes (isozymes) that is one of
clinical enzymes it is multiple forms of the enzymes
that have the same catalytic activity
They also differ in electrophoretic mobility and
responsibility to inhibitors
very important for diagnosis and indicate the
disease organs
3. source
Produce by the same gene but the
subunit undergo different post-
translation modification in different
organs
5. Lactate dehydrogenase (LDH)
Lactic acid Pyruvic acids
Lactase dehydrogenase
NAD NADH+H
It is level in plasma increases in :
1-Myocardia infarction
2- Viral hepatitis
3- leukaemia
6. The LDH is tetramer formed from 4 subunits each one
called protomer , protomer is 2 type M and H, so LDH
has 5 isoenzymes :
-LDH1 is formed of HHHH , it increases in myocardial infraction
-LDH2 is formed of HHHM , it increases in myocardial infraction
-LDH3 is formed of HHMM , it increases in luekaemia
-LDH4 is formed of HMMM , it increases in viral hepatitis
-LDH5 is formed of MMMM , it increases in viral hepatitis
7. Creatine phosphokinase(CPK)
Creatine Creatine phosphate
Creatine phosphokinase
ATP ADP + Pi
It is level in plasma increases in
1-Brain tumors
2-myocardial infraction
3-skeletal muscle disease
8. CPK is dimer formed from protomer ther are 2 type of
protomer B and M so CPK have 3 isoenzymes:
CPK BB which increase in brain tumors
CPK MB which increase in heart disease
CPKMM which increase in skeletal muscle disease
