Abstract Studies on anaerobiosis in marine invertebrates have shown that many rely on malate, octopine, or alanopine dehydrogenases, rather than lactate dehydrogenase, for cytosolic redox balance. These systems were studied by computer simulations with the assumption that these dehydrogenases maintain their substrates and products at instantaneous equilibrium. The simulations permit a study of the redox ratio (NADH/NAD +) as a function of the concentration of lactate, malate, or octopine. The redox ratio was found to increase as these products accumulated. It was substantially less in the simulations of malate and octopine dehydrogenases when compared to those of lactate dehydrogenase. This factor may be important for maintaining glycolysis in these organisms, and suggests an advantage for the use of octopine dehydrogenase rather than its analogue lactate dehydrogenase.