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Re: [APD] Malate

Steve Pushak writes:
"Does anyone know anything about how malate helps protect aquatic plants
from ethanol?"

I have to ask: do you have a lot of ethanol in your tank, and if so how do
you know? Are you planning on adding malate to help? I'm just really
curious as to the context of the question. For what it's worth, I've added
quite a lot of acetic acid to my tank deliberately (as a pH reducer)
without noticing any ill effects.

Anyway, to your question: I'm purely guessing here, but it might have
something to do with the way that ethanol reacts with NAD to form
acetaldehyde and NADH. Malate dehydrogenase (MDH) also converts NAD to NADH
when reducing malate into oxaloacetate. So, in effect, having ethanol will
reduce the supply of NAD necessary to reduce malate to oxaloacetate. And
the conversion of oxaloacetate back into malate to convert NADH back into
NAD is important too.

So perhaps having additional malate means that even in the presence of
ethanol you still get enough malate <--> oxaloacetate conversion to keep
the metabolism going. That is, the higher malate concentration means that
most NAD is consumed in the production of oxaloacetate rather than for
converting ethanol into acetaldehyde. And thus there's enough oxaloacetate
to convert back into malate to replenish the NAD supply.

Again, this is purely a guess. But it might at least give you a direction
to research.

- Jim

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