Question

what are efficiencies of alcohol dehydrogenases (ADH)?

Answer 1

Alcohol dehydrogenases (EC 1.1.99.36) are a class of zinc enzymes which catalyse the oxidation of primary and secondary alcohols to the corresponding aldehyde or ketone by the transfer of a hydride anion to NAD+ with release of a proton.

ethanol + acceptor acetaldehyde + reduced acceptor

They are abundant in the liver..

However, ethanol is not the only target of these enzymes. Retinol, steroids and fatty acid molecules are also affected.

The zinc atom binds to the substrate by the oxygen and polarises the carbonyl group of a substrate, hence favouring the transfer of a hydride ion from NADH. The histidine residue is then active by general base catalysis, allowing it to accept a proton from NADH. Simultaneously a hydride is transfered to the NAD in its specific region. The result is the transfer of a hydride ion to NAD and the oxidation of the alcohol substrate to an aldehyde.