Reduction of S-nitrosoglutathione by human alcohol dehydrogenase 3 is an irreversible reaction as analysed by electrospray mass spectrometry.

Human alcohol dehydrogenase 3/glutathione-dependent formaldehyde dehydrogenase was shown to rapidly and irreversibly catalyse the reductive breakdown of S-nitrosoglutathione. The steady-state kinetics of S-nitrosoglutathione reduction was studied for the wild-type and two mutated forms of human alcohol dehydrogenase 3, mutations that have previously been shown to affect the oxidative efficiency for the substrate S-hydroxymethylglutathione. Wild-type enzyme readily reduces S-nitrosoglutathione with a kcat/Km approximately twice the kcat/Km for S-hydroxymethylglutathione oxidation, resulting in the highest catalytic efficiency yet identified for a human alcohol dehydrogenase.