Editing Dehydrogenase (section)

=== Transferring a hydride and releasing a proton ===
Sometimes a dehydrogenase catalyzed reaction will look like this: AH + B<sup>+</sup> ↔ A<sup>+</sup> + BH when a [[hydride]] is transferred. [[File:Alcohol dehydrogenase.png|thumb|500px|Alcohol dehydrogenase oxidizes ethanol, with the help of the electron carrier NAD<sup>+</sup>, yielding acetaldehyde]]A represents the substrate that will be oxidized, while B is the hydride acceptor. Note how when the hydride is transferred from A to B, the A has taken on a positive charge; this is because the enzyme has taken two electrons from the substrate in order to reduce the acceptor to BH.

The result of a dehydrogenase catalyzed reaction is not always the acquisition of a positive charge. Sometimes the substrate loses a proton. This may leave free electrons on the substrate that move into a double bond. This happens frequently when an alcohol is the substrate; when the proton on the oxygen leaves, the free electrons on the oxygen will be used to create a double bond, as seen in the oxidation of ethanol to acetaldehyde carried out by alcohol dehydrogenase in the image on the right.<ref name=":4">{{Cite web
|url = https://qmul.ac.uk/sbcs/iubmb/enzyme/
|title = Enzyme Nomenclature: Recommendations of the Nomenclature Committee of the International Union of Biochemistry and Molecular Biology on the Nomenclature and Classification of Enzymes by the Reactions they Catalyse
|access-date = 29 March 2021
}}</ref>

Another possibility is that a water molecule will enter the reaction, contributing a [[hydroxide ion]] to the substrate and a proton to the environment. The net result on the substrate is the addition of one oxygen atom. This is seen for example in the oxidation of [[acetaldehyde]] to [[acetic acid]] by [[acetaldehyde dehydrogenase]], a step in the metabolism of ethanol and in the production of vinegar.