Isoenzymes

1. Isozymes and their role in
diagnosis of disease
Safalta Bhandari (1st year MBBS)

2. What are Isozymes?
• Multiple forms of an enzyme catalyzing the
same reaction
• Differ in their physical and chemical
properties

3. Role of enzyme in
diagnosis of disease
• Functional and Non-functional
enzyme
• Nonfunctional enzyme: Present in
plasma due to wear and tear of
various tissues
• Drastically increases during
necrosis or disease
• Assays of these enzymes are very
useful in diagnosis of disease
• Enzymes can act as diagnostic
markers of the underlying
diseases.

4. Role in diagnosis of disease
Enzymes in myocardial infarction
– Creatine phosphokinase: first enzyme to be
released into circulation within 6-18 hours
Peak value within 24-30 hours
Returns to normal level by 2nd or 3rd day
Isoenzym
e
Subunit Tissue of
origin
CPK1 BB Brain
CPK2 MB Heart
CPK3 MM Skeletal
Muscle

5. • Lactate
dehydrogenase:
generally rises from
the second day after
infarction
Peak value by the 3rd or
4th day
Reaches normal level
after 10-15 days
Isoenzy
me
Subunit
Constituti
on
Principal
tissue of
origin
 Note: Normally, LDH-2
concentration in blood is
greater than LDH-1
 but this pattern is
reversed in myocardial
infarction-Flipped Pattern

6. Electrophoresis of lactate dehydrogenase
With relative proportions of isoenzyme
A) Normal serum
B) Serum from a patient of myocardial infarction (LDH1
and LDH2 increases)

7. – Aspartate transaminase:
rises sharply after CPK
Peak value within 48 hours
Returns to normal level after
4-5 days

8. Enzymes in liver disease
• Alanine transaminase
• Aspartate transaminase
• Lactate dehydrogenase
Serum Gamma glutamyl transpeptidase is
useful in the diagnosis of alcoholic liver
disease

9. (B
)
Electrophoresis of lactate
dehydrogenase
With relative proportions of
isoenzyme
A) Normal serum
B) Serum from a patient of liver
disease (LDH5 Increases)

10. Enzymes in muscle disease
• Creatine phosphokinase
• Aldolase
• Aspartate transaminase

11. Enzymes in bone disease
• Alkaline Phosphatases-rickets, osteomalacia,
hyperparathyroidism, Paget’s disease.
• Acid Phosphatases-bony metastasis of
carcinoma prostate

12. Enzymes in cancers
• Acid phosphatases-prostatic carcinoma
• Neuron-specific enolases-lung cancer,
neuroblastoma, pheochromocytoma

14. • Urinary amylase- acute
pancreatitis
• B-N-Acetylgalactosidase- renal graft
dysfunction
• B-Glucuronidase- cancers of
urinary bladder, pancreas
• Lactate dehydrogenase- meningitis
• B glucuronidase- gastric
carcinoma
• Trypsin- Cystic fibrosis