Phosphoribosylanthranilate Isomerase

In enzymology, a phosphoribosylanthranilate isomerase (EC 5.3.1.24) is an enzyme that catalyzes the third step of tryptophan biosynthesis.

N-(5-phospho-beta-D-ribosyl)anthranilate 1-(2-carboxyphenylamino)-1-deoxy-D-ribulose 5-phosphate

Hence, this enzyme has one substrate, N-(5-phospho-beta-D-ribosyl)anthranilate, and one product, 1-(2-carboxyphenylamino)-1-deoxy-D-ribulose 5-phosphate.

This enzyme belongs to the family of isomerases, specifically those intramolecular oxidoreductases interconverting aldoses and ketoses. The systematic name of this enzyme class is N-(5-phospho-beta-D-ribosyl)anthranilate aldose-ketose-isomerase. Other names in common use include PRA isomerase, PRAI, IGPS:PRAI (indole-3-glycerol-phosphate, synthetase/N-5'-phosphoribosylanthranilate isomerase complex), and N-(5-phospho-beta-D-ribosyl)anthranilate ketol-isomerase. In yeast it is expressed from the TRP1 gene. This enzyme participates in phenylalanine, tyrosine and tryptophan biosynthesis.