Are there any mammals that are know to be able to safely digest methanol? I can find lots of statements online to the effect that there are microorganisms which actually find it nutritious, and explanations of its toxicity to humans that state that it’s not the methanol itself but the byproducts of its metabolism in the liver (formaldehyde and formic acid) that are harmful, but nothing about any higher organisms that are able to handle it in large quantities.
Methanol is processed by one of the alcohol dehydrogenase enzymes and, as you noted, the byproducts formaldehyde and formic acid cause the toxicity.
Ethanol is converted to acteylaldehyde by the same enzyme. Acetylaldehyde is further catabolized to acetic acid (vinegar) by a different alcohol dehydrogenase enzyme. Further catabolism of acetic acid eventually results in acetyl Co-A and then water and carbon dioxide.
The digestive process in mammals produces some small amount of ethanol and your body needs some way to get rid of it. The enzymes that carry out these steps are highly conserved and some protein sequence homology is noted even in bacteria. It is unlikely that any mammal does not have these enzyme pathways and thus methanol would be toxic to mammals.
Bacterial metabolism of methanol is through entirely different pathways which mammals lack.
Thank you for the response, Iggy. So, it sort of sounds like you’re saying that mammals can process ethanol because they have to anyway, but they can’t process methanol because they don’t have any reason to?
What sources of methanol are there in nature? The only source I can find explicitly described on Wikipedia is the destructive distillation of wood, but that doesn’t sound like something that could happen naturally outside of a forest fire. Is methanol ever produced as a byproduct of the digestion of cellulose?
Certain archaebacteria, methanogens, produce methane (CH[sub]4[/sub]) as a waste product.
Some other bacteria can utilize that methane as a carbon source. They oxidize the methane to methanol (CH[sub]3[/sub]OH) as an intermediate step in their metabolism.
Trace amounts of methanol are also produced in non-enzyme mediated reactions during fermentation processes. Occasionally news reports surface of a bad batch of homemade booze causing blindness due to high methanol content.