A flavoprotein (FAD). The enzyme, found in plants and some bacteria, catalyses the reversible conversion of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate using NADH as the electron donor. It play an important role in folate metabolism by regulating the distribution of one-carbon moieties between cellular methylation reactions and nucleic acid synthesis. These proteins either contain a C-terminal domain that does not mediate allosteric regulation (as in plants) or lack this domain entirely (as in Escherichia coli). As a result, the plant enzymes are not inhibited by S-adenosyl-L-methionine, unlike other eukaryotic enzymes, and catalyse a reversible reaction. cf. EC 220.127.116.11
, methylenetetrahydrofolate reductase (NADPH); EC 18.104.22.168
, methylenetetrahydrofolate reductase [NAD(P)H]; and EC 22.214.171.124
, methylenetetrahydrofolate reductase (ferredoxin).