In type la maple syrup urine disease, gene mutation seen is

In type la maple syrup urine disease,
gene mutation seen is ?
a) Ela
b) Elb
c) E2
d) E3
Correct Answer - A
Ans. is ‘a’ i.e., Ela [Ref Harper 27"/e ch. 29; Nelson 18th/e ch.
85.6; Medical biochemistry by sheriff 1"/e p. 513]
Metabolic disorders of branched-chain amino acid catabolism
As the name implies, the odor of urine in maple syrup urine disease
(branched-chain ketonuria) suggests maple syrup or burnt sugar.
Decarboxylation of leucine, isoleucine, and valine is accomplished
by a complex enzyme system (branched-chain a-ketoacid
dehydrogenase) using thiamine pyrophosphate (vitamin 81) as a
conzyme.
This mitochondrial enzyme consists of four subunits: Ha, El (3, E2,
and E3. Deficiency of this enzyme system causes MSUD. Based on
clinical findings and response to thiamine administration, five
phenotypes MSUD have been identified classical, intermediate,
intermittent, thiamine responsive and E3 deficiency. All forms of
MSUD are inherited as an autosomal recessive trait