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
6.3.1.21, phosphoribosylglycinamide formyltransferase 2, utilizes formate. In vertebrates this activity is catalysed by a trifunctional enzyme that also catalyses the activities of EC
6.3.4.13, phosphoribosylamine---glycine ligase and EC
6.3.3.1, phosphoribosylformylglycinamidine cyclo-ligase.
