1.5.1.15 | 5,10-methylenetetrahydrofolate + NAD+ = 5,10-methenyltetrahydrofolate + NADH + H+ |
the reaction catalyzed by Escherichia coli MTHFR can be divided into a reductive half-reaction and an oxidative half-reaction, respectively, in which the FAD cofactor acts as an intermediate electron acceptor and donor. The enzyme employs a ping-pong bi-bi kinetic mechanism, in which the release of NAD+, the product of the first half-reaction, precedes binding of the substrate CH2-H4folate in the second half-reaction. Rapid-reaction kinetic studies have established that the enzyme catalyzes these half-reactions at rates consistent with the observed rate of overall turnover. Proposed mechanism for the oxidative half-reaction, overview |
760434 |