Background of the antigen
Phosphoribosyl pyrophosphate amidotransferase (PPAT) is a regulatory allosteric enzyme that catalyzes the first step of de novo purine nucleotide biosynthesis. The genes for PPAT and PAICS/AIRC, (a bifunctional enzyme catalyzing steps six and seven in the purine nucleotide biosynthesis pathway), are located in close proximity on chromosome 4.