This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Phenylalanine and Tyrosine metabolism Detail, Subject name: Biochemistry
Ochronosis is caused by 
Select and explain. 
A. Tyrosinemia Type I, B. Maple syrup urine disease, C. Alkaptonuria, D. Phenylketonuria
C: Alkaptonuria
Answer: C: Alkaptonuria 
Explanation: In Alkaptonuria there is defect in catabolism of Tyrosine and Phenylalanine Enzyme deficient-Homogentisate Dioxygenase Homogentisic acid is an intermediate in the catabolism of Tyrosine Deposition of black pigments (polymerization of Homogentisic acid occurring in body over years) in joints, cailage and collagenous tissue is known as Ochronosis. DEPOSITION OF BLACK PIGMENTS