LDH has how many isoenzymes
a) 3, based on B and M polypeptide subunits
b) 5, based on B and M polypeptide subunits
c) 7, based on H and M polypeptide subunits
d) 5, based on H and M polypeptide subunits
Correct Answer - D
Ans. is ‘d’ i.e., 5, based on H and M polypeptide subunits
lRef: Dinesh puri 3’d/e p. 1221
LDH is a tetramer with two types of polypeptide units : (H) (for
heart) and M (for muscle).
lt has five isoenzymes:
LDH 1 (HHHH), LDH 2 (HHHM), LDH3 (HHMM), LDH 4
(HMMM), and LDH s (MMMM).
LDH-I and LDH-2 are the predominant isozymes in myocardium,
therefore these are raised in MI (LDHf > LDH2),
LDH-f is more specific for myocardium (as it has 4H) than
LDH-2.
The predominent isoenzyme in liver is LDH5; Hence LDH5 is
raised in liver diseases like viral hepatitis.
Normal LDH pattern on electrophoresis is LDH2 > LDHI > LDH
3 > LDH 4 > LDH5.
In MI LDHI is raised more thar LDHz, So, pattern becomes
LDHI > LDH2 > LDH3 > LDH4 > LDH5.
Increase in total LDH level is also seen in hemolytic anemia,
hepatocellular damage, muscular dystrophies, leukemia,
carcinomas, cerebrovascular accident, pancreatitis, kidney
disease, intestinal and pulmonary infarction, megaloblastic
anemia and infectious mononucleosis. Therefore study of specific
isozyme is more significant.