Abstract
Cytochromes cH and cL were autoreduced at high pH (pK greater than 10) and the autoreduced cytochromes reacted with CO. The autoreduction was first-order with respect to oxidized cytochrome c and was reversible by lowering the pH. Pure methanol dehydrogenase reduced cytochrome c (in the absence of methanol) by lowering the pK for autoreduction to less than 8.5. A mechanism is proposed for the autoreduction of cytochrome c and its involvement in the reaction with methanol dehydrogenase.