Question

Lesch–Nyhan syndrome is caused by deficiency of which enzyme?

• A. Orotate Phosphoribosyltransferase
• B. Uracil phosphoribosyltransferase
• C. Quinolinate Phosphoribosyltransferase
• D. Hypoxanthine-guanine phosphoribosyltransferase (HGPRT)

Answer 1

The Correct Option is D

Lesch–Nyhan syndrome is a rare and genetic disorder characterized by neurological and behavioral abnormalities and the overproduction of uric acid. It is an X-linked recessive disorder caused by a deficiency of the enzyme Hypoxanthine-guanine phosphoribosyl transferase (HGPRT).

The HGPRT enzyme is crucial for the purine salvage pathway, which allows the reuse of purines from degraded nucleic acids to synthesize new nucleotides. When HGPRT activity is deficient, hypoxanthine and guanine accumulate and are converted to uric acid, leading to hyperuricemia. This enzymatic defect is responsible for the symptoms associated with Lesch–Nyhan syndrome.

Pathophysiology:

• HGPRT deficiency -> inability to salvage hypoxanthine and guanine -> accumulation of uric acid.
• Accumulated uric acid leads to symptoms like gout, kidney stones, and neurological/behavioral disorders.

In summary, Lesch–Nyhan syndrome is caused by a deficiency of Hypoxanthine-guanine phosphoribosyltransferase (HGPRT), which plays a crucial role in nucleotide salvage. The lack of this enzyme results in increased production and accumulation of uric acid.