Which enzyme deficiency causes maple syrup urine disease?

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Multiple Choice

Which enzyme deficiency causes maple syrup urine disease?

Maple syrup urine disease arises when the branched-chain α-ketoacid dehydrogenase complex is defective. This enzyme catalyzes the oxidative decarboxylation of the α-keto acids produced when the branched-chain amino acids are transaminated—valine, leucine, and isoleucine. Without this decarboxylation step, these branched-chain metabolites accumulate, leading to the characteristic maple syrup odor and neurological symptoms. Among the options, the enzyme that performs this decarboxylation of the branched-chain α-keto acids is the correct match. The other enzymes are involved in different metabolic disorders: phenylalanine hydroxylase defects cause phenylketonuria, homogentisic acid oxidase defects cause alkaptonuria, and tyrosine aminotransferase defects relate to tyrosinemia.

Maple syrup urine disease arises when the branched-chain α-ketoacid dehydrogenase complex is defective. This enzyme catalyzes the oxidative decarboxylation of the α-keto acids produced when the branched-chain amino acids are transaminated—valine, leucine, and isoleucine. Without this decarboxylation step, these branched-chain metabolites accumulate, leading to the characteristic maple syrup odor and neurological symptoms. Among the options, the enzyme that performs this decarboxylation of the branched-chain α-keto acids is the correct match. The other enzymes are involved in different metabolic disorders: phenylalanine hydroxylase defects cause phenylketonuria, homogentisic acid oxidase defects cause alkaptonuria, and tyrosine aminotransferase defects relate to tyrosinemia.

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