This family includes a variety of pterin binding enzymes that all adopt a TIM barrel fold. The family includes dihydropteroate synthase EC:2.5.1.15 as well as a group methyltransferase enzymes including methyltetrahydrofolate, corrinoid iron-sulfur protein methyltransferase (MeTr) Swiss:Q46389 that catalyses a key step in the Wood-Ljungdahl pathway of carbon dioxide fixation. It transfers the N5-methyl group from methyltetrahydrofolate (CH3-H4folate) to a cob(I)amide centre in another protein, the corrinoid iron-sulfur protein. MeTr is a member of a family of proteins that includes methionine synthase and methanogenic enzymes that activate the methyl group of methyltetra-hydromethano(or -sarcino)pterin [2].

1: Crystal structure of the anti-bacterial sulfonamide drug target dihydropteroate synthase. Achari A, Somers DO, Champness JN, Bryant PK, Rosemond J, Stammers DK Nat Struct Biol 1997;4:490-497. PMID:9187658

2: Crystal structure of a methyltetrahydrofolate- and corrinoid-dependent methyltransferase. Doukov T, Seravalli J, Stezowski JJ, Ragsdale SW; Structure Fold Des 2000;8:817-830. PMID:10997901