Reduced cytochrome c oxidase extracted from the liver of Rat

Reduced cytochrome c oxidase extracted from the liver of Rattus norvegicus is used in the lab to measure the effect of pH on enzymatic activity. Why do we use reduced (as opposed to oxidized) cytochrome c as the substrate for our reaction?

Solution

Cytochrome c oxidase activity of the liver of Rattus norvegicus decrease at higher pH. At different pH conditions, the oxidase activity of the enzyme decreases and sometime fully reversible. Km value of the enzyme also significantly affected at differently pH’s.

Hence, we have to reduce cytochrome c as the substrate for our reaction