Human mitochondrial MTHFD2 is a dual redox cofactor-specific methylenetetrahydrofolate dehydrogenase/methenyltetrahydrofolate cyclohydrolase

MTHFD2 exhibits NADP+-dependent dehydrogenase activity with 5,10-CH2-THF pentaglutamate. a Compartmentation of mammalian one-carbon metabolism. MTHFD1 is the cytoplasmic trifunctional C1-THF synthase that catalyzes 10-formyl-THF synthetase, 5,10-methenyl-THF cyclohydrolase, and 5,10-methylene-THF dehydrogenase activities. In mammalian mitochondria, bifunctional MTHFD2 or MTHFD2L enzymes catalyze 5,10-methenyl-THF cyclohydrolase and 5,10-methylene-THF dehydrogenase activities, and monofunctional MTHFD1L catalyzes the 10-formyl-THF synthetase reaction. SHMT1 and SHMT2 represent cytoplasmic and mitochondrial serine hydroxymethyltransferase isozymes, respectively. Gray ovals represent putative metabolite transporters. b, c Purified MTHFD2 was assayed for NAD+- and NADP+-dependent 5,10-CH2-THF dehydrogenase activity with saturating concentrations of CH2-H4PteGlu1 or CH2-H4PteGlu5 (insets, 5,10-CH2-THF dehydrogenase activity of MTHFD2L; data from ref. 11). CH2-H4PteGlu1 and CH2-H4PteGlu5 concentrations were 354 and 429 μM, respectively. NAD+ and NADP+ concentrations were 1.0 and 6.0 mM, respectively. NAD+-dependent reactions also included 5 mM MgCl2 and 25 mM Pi. NADP+-dependent reactions included only 5 mM MgCl2. Each column represents the mean？±？S.E. of triplicate determination