I have a related question: I am trying to understand the difference between:
Aldehyde Dehydrogenase: (NAD+) + H20 + Acetaldehyde -> NADH + (H+) + Acetic Acid
and
Acetaldehyde Dehydrogenase: Acetaldehyde + NAD+ + Coenzyme A ↔ Acetyl-CoA + NADH + H+
From what I have shared (taken from wikipedia, or in the case of aldehyde dehydrogenase, interpreted from wikipedia), they seem obviously to code for different reactions. But here is what Wikipedia says about human
acetaldehyde dehydrogenase:
As far as I can tell, all of these genes code for aldehyde dehydrogenases, not acetaldehyde dehydrogenases, meaning that they code for enzymes that perform the first function I listed and not the second. I understand that it is possible for acetic acid to take part in the formation of Acetyl-CoA through two more reactions:
1. Acetic Acid does the acid thing (forgive my lack of chemistry terminology) and loses a hydrogen, becoming Acetate.
2. Acetate is then added to CoA by Acetyl CoA Synthetase in this reaction:
Acetate + ATP + CoA -> Acetyl CoA + AMP + PPi
In short, it appears that using the aldehyde dehydrogenase pathway to form Acetyl-CoA ends up costing us the converstion of an ATP to AMP, while the acetaldehyde dehydrogenase pathway does not.
So I am confused when the enzyme that codes for
ALDH2 (Aldehyde Dehydrogenase 2 Family, Mitochondrial) is also known as "Acetaldehyde Dehydrogenase 2." Should I just assume that the reaction for acetaldehyde dehydrogenase only applies to some bacteria, and assume that in humans the acetaldehyde dehydrogenase reaction encompasses anything happening within these steps: Acetaldehyde -> Acetic Acid -> Acetate -> Acetyl-CoA? That is what seems mostly likely to me, but I can't find anyone who comes out and says it.
Thank you in advance!