Amidophosphoribosyltransferase (ATase), also known as glutamine phosphoribosylpyrophosphate amidotransferase (GPAT), is an enzyme that in humans is encoded by the PPAT (phosphoribosyl pyrophosphate amidotransferase) gene.
ATase is an enzyme that converts α-phosphoribosylpyrophosphate (α-PRPP) into 5-β-phosphoribosylamine. The enzyme uses the ammonia group from the glutamine side-chain. This is the committing step in de novo purine synthesis. It is allosterically inhibited by AMP, GMP, and IMP. 6TGMP (6-thioguanine monophosphate) is a pseudo inhibitor for ATase
ATase is a member of the purine/pyrimidine phosphoribosyltransferase family. This protein is a regulatory allosteric enzyme that catalyzes the first step of de novo purine nucleotide biosynthesis.
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