Phosphoribosylglycinamide formyltransferase (EC 2.1.2.2) (GART) [1] catalyzes the third step in de novo purine biosynthesis, the transfer of a formyl group to 5'-phosphoribosylglycinamide. In higher eukaryotes, GART is part of a multifunctional enzyme polypeptide that catalyzes three of the steps of purine biosynthesis. In bacteria, plants and yeast, GART is a monofunctional protein of about 200 amino-acid residues.

In the Escherichia coli enzyme, an aspartic acid residue has been shown to be involved in the catalytic mechanism. The region around this active site residue is well conserved in GART from prokaryotic and eukaryotic sources and can be used as a signature pattern.

Mammalian formyltetrahydrofolate dehydrogenase (EC 1.5.1.6) [2] is a cytosolic enzyme responsible for the NADP-dependent decarboxylative reduction of 10-formyltetrahydrofolate into tetrahydrofolate. It is a protein of about 900 amino acids consisting of three domains; the N-terminal domain (200 residues) is structurally related to GARTs.

Escherichia coli methionyl-tRNA formyltransferase (EC 2.1.2.9) (gene fmt) [3] is the enzyme responsible for modifying the free amino group of the aminoacyl moiety of methionyl-tRMA(fMet). The central part of fmt seems to be evolutionary related to GART's active site region.