Amidophosphoribosyltransferase

Amidophosphoribosyltransferase (ATase), also known as glutamine phosphoribosylpyrophosphate amidotransferase (GPAT), is an enzyme that plays a crucial role in the biosynthesis of purine nucleotides. This enzyme is encoded by the PPAT gene in humans.

Function

Amidophosphoribosyltransferase catalyzes the first step in the purine biosynthetic pathway, converting glutamine and 5-phosphoribosyl-1-pyrophosphate (PRPP) to 5-phosphoribosylamine (PRA) and glutamate. This reaction is the committed step in purine biosynthesis, meaning it is the point at which the pathway is dedicated to producing purine nucleotides.

Structure

The enzyme is a multimer composed of multiple subunits. Each subunit contains a glutaminase domain and a synthetase domain. The glutaminase domain hydrolyzes glutamine to glutamate and ammonia, while the synthetase domain combines PRPP and ammonia to form PRA.

Clinical significance

Mutations in the PPAT gene can lead to disorders of purine metabolism, such as Lesch-Nyhan syndrome and gout. These conditions are characterized by an overproduction of purine nucleotides, leading to an excess of uric acid, the end product of purine metabolism.

File:Amidophosphoribosyltransferase 3D structure.png

3D structure of amidophosphoribosyltransferase

See also

• Purine metabolism
• Purine nucleotide cycle
• Lesch-Nyhan syndrome
• Gout

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