In contrast to MTHFD1 that has trifunctional methylenetetrahydrofolate dehydrogenase, methenyltetrahydrofolate cyclohydrolase, and formyltetrahydrofolate synthetase enzymatic activities, MTHFD1L only has formyltetrahydrofolate synthetase activity.
These folate-dependent biosynthetic reactions include the transfer of methyl groups from 5-methyltetrahydrofolate to homocysteine to form formyl groups from 10-formyltetrahydrofolate to N-formylmethionine in initiator tRNAs.