**Question:** Enzyme deficiency in albinism is:

A. Tyrosinase
B. Tyrosine aminotransferase
C. Tyrosine hydroxylase
D. Phenylalanine hydroxylase

**Core Concept:**

Albinism is a genetic disorder characterized by a deficiency in melanin production, resulting in skin, hair, and eye pigmentation abnormalities. The primary enzymes involved in melanin synthesis are:

1. Tyrosinase (EC 1.14.18.1) - catalyzes the conversion of L-tyrosine to L-3,4-dihydroxyphenylalanine (DOPA), which is further processed to melanin.
2. Tyrosine aminotransferase (EC 2.6.1.57) - converts L-tyrosine into L-3,4-dihydroxyphenylalanine (DOPA) via transamination, which is then converted to melanin by tyrosinase.
3. Tyrosine hydroxylase (EC 1.14.16.2) - catalyzes the rate-limiting step in dopamine synthesis from L-tyrosine. Dopamine is a precursor to melanin.
4. Phenylalanine hydroxylase (EC 1.14.16.1) - converts phenylalanine into tyrosine, which is also a precursor to melanin.

**Why the Correct Answer is Right:**

In albinism, there is a deficiency in the synthesis of melanin due to a reduced activity of tyrosinase. Tyrosinase plays a critical role in the conversion of L-tyrosine to L-3,4-dihydroxyphenylalanine (DOPA), which subsequently leads to a deficiency in melanin production.

**Why Each Wrong Option is Incorrect:**

A) Tyrosine aminotransferase (option B) and Phenylalanine hydroxylase (option D) are involved in the synthesis of dopamine and tyrosine, respectively. However, neither of these enzymes is directly responsible for melanin synthesis.

B) Tyrosine hydroxylase (option C) is important in the synthesis of dopamine, but it is not directly related to melanin synthesis. Tyrosinase is the enzyme responsible for melanin synthesis.

In summary, the deficiency in melanin production in albinism is primarily caused by reduced tyrosinase activity, not by deficiencies in the mentioned enzymes (A, B, C, and D).

**Clinical Pearls:**

Albinism is a rare genetic disorder characterized by skin, hair, and eye color abnormalities due to melanin deficiency. Tyrosinase is essential for melanin production, and its reduction leads to the observed features of albinism.

Understanding the correct role of enzymes in melanin synthesis is crucial for understanding the pathogenesis of albinism and interpreting its clinical features.