The effect of ethanol on the activity of pepsin

Athel Cornish-Bowden athel at BIGFOOT.COM
Tue May 20 04:52:31 EST 1997

"SpaceboY" <andre at> asked:

>Can someone explain how ethanol may affect the activity of pepsin. I have
>found that the rate of reaction catalysed by pepsin is greatly reduced
>even by adding ethanol of just 1% concentration.

It's now nearly 30 years since I did any experimental work on pepsin, so my
knowledge is certainly out of date, but I doubt whether the current view of
something like this would be too different from what it was then, and I
find this observation very surprising.

Pepsin (crystalline pig pepsin) can certainly stand quite high
concentrations of other organic solvents (e.g. 30% dimethylformamide).
Moreover, methanol is only a very feeble inhibitor of pepsin (J. Tang, J.
Biol. Chem. 240, 3810 (1965)), and it's hard to believe ethanol is so
different. If I remember rightly the early methods of making pepsin
crystallize involved adding ethanol, and it didn't seem to do it any harm.

Athel Cornish-Bowden

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