Lack of Homogentisate oxidase enzyme causes: (A) Phenylketonuria, (B) Alkaptonuria, (C) Maple syrup urine disease, (D) Homocystinuria
Answer is B. (B) Alkaptonuria # ALKAPTONURIA: The defective enzyme in alkaptonuria is homogentisate oxidase in tyrosine metabolism. Homogentisate accumulates in tissues & blood, gets oxidized to the corresponding quinones, which polymerize to give black or brown colour. For this reason, the urine of alkaptonuric patients resembles coke in colour.