1.5.1.50 evolution the enzyme belong to the short-chain dehydrogenase/reductase (SDR) family of enzymes. Despite the overall low sequence identity among members of the SDR family (about 15-30%), a central catalytic YX3K motif is highly conserved, as is an N-terminal glycine motif (TGX3GXG), involved in cofactor binding and recognition. The pteridine reductases in the SDR family have an arginine in place of the glycine at position 6 in this motif (TGX3RXG) -, 765008 1.5.1.50 additional information enzyme structure modelling -, 765008 1.5.1.50 physiological function dihydroneopterin triphosphate epimerase folX and dihydromonapterin reductase folM are essential for Pseudomonas aeruginosa phenylalanine hydroxylase function in Escherichia coli 704330 1.5.1.50 physiological function FolM produces tetrahydromonapterin (H4MPt), the cofactor of phenylalanine hydroxylase in specific bacteria. Although PA3437 is originally defined as FolM and is encoded in a gene cluster with other genes involved in tetrahydromoapterin (H4MPt) biosynthesis (FolE and FolX), its high activity with dihydrofolate (H2F) implicates this pteridine reductase as a potential backup dihydrofolate reductase (DHFR) -, 765008 1.5.1.50 physiological function FolM produces tetrahydromonapterin (H4MPt), the cofactor of phenylalanine hydroxylase in specific bacteria. FolM from Escherichia coli displays activity only with the dihydro form of its pterin substrate 765008