In enzymology, a methylenetetrahydrofolate dehydrogenase (NAD+) () is an enzyme that catalyzes a chemical reaction. 5,10-methylenetetrahydrofolate + NAD+ 5,10-methenyltetrahydrofolate + NADH + H+ Thus, the two substrates of this enzyme are 5,10-methylenetetrahydrofolate and NAD+, whereas its 3 products are 5,10-methenyltetrahydrofolate, NADH, and H+. This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-NH group of donors with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is 5,10-methylenetetrahydrofolate:NAD+ oxidoreductase. This enzyme is also called methylenetetrahydrofolate dehydrogenase (NAD+). This enzyme participates in one carbon pool by folate. Structural studies As of late 2007, two structures have been solved for this class of enzymes, with PDB accession codes and . References EC 1.5.1 NADH-dependent enzymes Enzymes of known structure