Alkaptonuria is due to deficiency of which enzyme?

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Multiple Choice

Alkaptonuria is due to deficiency of which enzyme?

Alkaptonuria results from a block in tyrosine degradation at the step that converts homogentisic acid to maleylacetoacetate. When homogentisic acid oxidase is deficient, this substrate accumulates and is excreted in the urine, where it oxidizes and polymerizes to give the characteristic dark color, and it can deposit in connective tissues over time (ochronosis). This makes this enzyme the correct cause of alkaptonuria because the buildup of homogentisic acid directly explains the observed symptoms. Other enzymes listed are involved in different metabolic conditions. For example, phenylalanine hydroxylase deficiency causes phenylketonuria, and fumarylacetoacetate hydrolase deficiency leads to tyrosinemia type I, not alkaptonuria. The ketoacid decarboxylase family includes enzymes acting in various amino acid pathways but does not specifically explain the tyrosine degradation block seen in alkaptonuria.

Alkaptonuria results from a block in tyrosine degradation at the step that converts homogentisic acid to maleylacetoacetate. When homogentisic acid oxidase is deficient, this substrate accumulates and is excreted in the urine, where it oxidizes and polymerizes to give the characteristic dark color, and it can deposit in connective tissues over time (ochronosis). This makes this enzyme the correct cause of alkaptonuria because the buildup of homogentisic acid directly explains the observed symptoms.

Other enzymes listed are involved in different metabolic conditions. For example, phenylalanine hydroxylase deficiency causes phenylketonuria, and fumarylacetoacetate hydrolase deficiency leads to tyrosinemia type I, not alkaptonuria. The ketoacid decarboxylase family includes enzymes acting in various amino acid pathways but does not specifically explain the tyrosine degradation block seen in alkaptonuria.

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