In Tyrosinemia Type II, deficiency of which enzyme?

• A. Tyrosine Aminotransferase
• B. Fumarylacetoacetate Hydrolase
• C. Tyrosine Hydroxylase
• D. Homogentisate Oxidase

Answer: (A)

Tyrosinemia Type II results from a deficiency of tyrosine aminotransferase, the liver enzyme that normally converts tyrosine to p-hydroxyphenylpyruvate in tyrosine degradation. Without this step, tyrosine accumulates in blood and tissues, leading to ocular and skin changes such as corneal lesions and hyperkeratotic plaques on the hands and feet. The other enzymes listed are linked to different conditions: fumarylacetoacetate hydrolase deficiency causes Tyrosinemia Type I with severe liver involvement; tyrosine hydroxylase deficiency affects catecholamine synthesis; homogentisate oxidase deficiency causes alkaptonuria.