10-Formyltetrahydrofolate (10-CHO-THF) is form of tetrahydrofolate that acts as a donor of formyl groups in anabolism. In particular, 10-CHO-THF is used as a substrate in a number of formyltransferase reactions. It plays an important role in purine biosynthesis, where 10-CHO-THF is a substrate for phosphoribosylaminoimidazolecarboxamide formyltransferase, as well as in the formylation of the methionyl initiator tRNA (fMet-tRNA), when 10-CHO-THF is a substrate for methionyl-tRNA formyltransferase. 10-Formyltetrahydrofolate is a substrate for Trifunctional purine biosynthetic protein adenosine-3, Bifunctional methylenetetrahydrofolate dehydrogenase/cyclohydrolase (mitochondrial), 10-formyltetrahydrofolate dehydrogenase, Folylpolyglutamate synthase (mitochondrial), Bifunctional purine biosynthesis protein PURH and C-1-tetrahydrofolate synthase (cytoplasmic).