Methanol dehydrogenase

In enzymology, a methanol dehydrogenase is an enzyme that catalyzes the chemical reaction:

methanol ${\displaystyle \rightleftharpoons }$ formaldehyde + 2 electrons + 2H⁺

Shows the reaction of methanol to formaldehyde catalyzed by MDH.[1]

How the electrons are captured and transported depends upon the kind of methanol dehydrogenase. There are three main types of MDHs: NAD+-dependent MDH, pyrrolo-quinoline quinone dependent MDH, and oxygen-dependent alcohol oxidase.[1] A common electron acceptor in biological systems is nicotinamide adenine dinucleotide (NAD⁺) and some enzymes use a related molecule called nicotinamide adenine dinucleotide phosphate (NADP⁺). An NAD⁺-dependent methanol dehydrogenase(EC 1.1.1.244) was first reported in a Gram-positive methylotroph[2] and is an enzyme that catalyzes the chemical reaction

methanol + NAD⁺ ${\displaystyle \rightleftharpoons }$ formaldehyde + NADH + H⁺

Thus, the two substrates of this enzyme are methanol and NAD⁺, whereas its 3 products are formaldehyde, NADH, and H⁺.

This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD⁺ or NADP⁺ as acceptor. The systematic name of this enzyme class is methanol:NAD⁺ oxidoreductase. This enzyme participates in methane metabolism.

Prior to the discovery of this enzyme, methanol oxidation in Gram-negative bacteria had been shown to be by way of an (NAD⁺) independent alcohol dehydrogenase found originally in Pseudomonas M27. This enzyme (EC. 1.1.99.8) contains a prosthetic group called Pyrrolo Quinoline Quinone (PQQ) that accepts the electrons generated from methanol oxidation and passes these electrons to cytochrome c.[3]