10-Formyl-tetrahydrofolate (10-CHO-THF) is form of tetrahydrofolate that acts as a donor of formyl groups in anabolism. In these reactions 10-CHO-THF is used as a substrate in formyltransferase reactions. This is important 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), 10-CHO-THF is a substrate for methionyl-tRNA formyltransferase.
10-CHO-THF is produced by the enzymes methenyltetrahydrofolate cyclohydrolase and formate-tetrahydrofolate ligase. It can be converted back into tetrahydrofolate and formate by formyltetrahydrofolate deformylase.