-!- In some bacteria, a single protein catalyzes both this activity and that of EC 6.3.2.12, the combined activity of which leads to the formation of the coenzyme polyglutamated tetrahydropteroate (H(4)PteGlu(n)), i.e. various tetrahydrofolates (H(4)folate). -!- In contrast, the activities are located on separate proteins in most eukaryotes studied to date. -!- In Arabidopsis thaliana, this enzyme is present as distinct isoforms in the mitochondria, the cytosol and the chloroplast. -!- Each isoform is encoded by a separate gene, a situation that is unique among eukaryotes. -!- As the affinity of folate-dependent enzymes increases markedly with the number of glutamic residues, the tetrahydropteroyl polyglutamates are the preferred coenzymes of C(1) metabolism. -!- The enzymes from different sources (particularly eukaryotes versus prokaryotes) have different substrate specificities with regard to one-carbon substituents and the number of glutamate residues present on the tetrahydrofolates.