Question

Given below are two statements:
Statement I: Alkaptonuria is known as an inborn error of metabolism associated with certain amino acids
Statement II: The mutation of homogentisate 1,2-dioxygenase (HGD) gene leads to abnormal metabolism of certain amino acids like phenylalanine and tyrosine that leads to alkaptonuria
In the light of the above statements, choose the most appropriate answer from the options given below

• A. Both Statement I and Statement II are true
• B. Both Statement I and Statement II are false
• C. Statement I is true but Statement II is false
• D. Statement I is false but Statement II is true

Hint:

Inborn Errors of Tyrosine/Phenylalanine:
PKU $\rightarrow$ Phenylalanine Hydroxylase.
Alkaptonuria $\rightarrow$ Homogentisate 1,2-Dioxygenase.
Albinism $\rightarrow$ Tyrosinase.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Inborn errors of aromatic amino acid catabolism result from autosomal recessive genetic enzyme deficiencies.
Key Formula or Approach:
\[ \text{Phenylalanine} \longrightarrow \text{Tyrosine} \longrightarrow \text{Homogentisate} \xrightarrow{\text{Homogentisate 1,2-Dioxygenase (Deficient)}} \text{Ochronosis / Alkaptonuria} \]

Step 2: Detailed Explanation:
1. Statement I: Alkaptonuria is the classic autosomal recessive inborn error of metabolism described by Sir Archibald Garrod in 1902, characterized by dark urine (on standing/alkalization), ochronosis (connective tissue pigmentation), and arthritis. Hence, Statement I is true.
2. Statement II: It is caused by loss-of-function mutations in the Homogentisate 1,2-Dioxygenase (HGD) gene on chromosome 3q, which blocks the degradation of homogentisic acid in the catabolic pathway of phenylalanine and tyrosine. Hence, Statement II is true.

Step 3: Final Answer:
Therefore, Both Statement I and Statement II are true, corresponding to option (A).