Two enzymes are known to catalyse the third step in de novo purine biosynthesis. This enzyme utilizes 10-formyltetrahydrofolate as the formyl donor, while the other enzyme, EC 188.8.131.52
, phosphoribosylglycinamide formyltransferase 2, utilizes formate. In vertebrates this activity is catalysed by a trifunctional enzyme that also catalyses the activities of EC 184.108.40.206
, phosphoribosylamine---glycine ligase and EC 220.127.116.11
, phosphoribosylformylglycinamidine cyclo-ligase.