InterPro domain: IPR004810

An Escherichia coli gene designated purU has been identified and characterised. The gene codes for a 280-amino-acid protein, PurU ( P37051 , 3.5.1.10 ). PurU is an enzyme that catalyses the hydrolysis of 10-formyltetrahydrofolate (formyl-FH4) to FH4 and formate [ 1 , 2 ].

10-formyltetrahydrofolate + H(2)O = formate +tetrahydrofolate

Formyl-FH4 hydrolase generates the formate that is used by purT-encoded 5'-phosphoribosylglycinamide transformylase for step three of de novo purine nucleotide synthesis. Formyl-FH4 hydrolase, a hexamer of 32kDa subunits, is activated by methionine and inhibited by glycine. Heterotropic cooperativity is observed for activation by methionine in the presence of glycine and for inhibition by glycine in the presence of methionine. These results suggest that formyl-FH4 hydrolase is a regulatory enzyme whose main function is to balance the pools of FH4 and C1-FH4 in response to changing growth conditions. The enzyme uses methionine and glycine to sense the pools of C1-FH4 and FH4, respectively.

1. Formyltetrahydrofolate hydrolase, a regulatory enzyme that functions to balance pools of tetrahydrofolate and one-carbon tetrahydrofolate adducts in Escherichia coli. J. Bacteriol. 177, 1292-8
2. purU, a source of formate for purT-dependent phosphoribosyl-N-formylglycinamide synthesis. J. Bacteriol. 175, 7066-73