Action of bovine serum albumin on cytochrome c oxidase activity and proton pumping: a role for fatty acids in enzyme function?

Bovine serum albumin (BSA) at micromolar concentrations causes a red shift of the Soret band of bovine cytochrome c oxidase with a slow biphasic time course. It also inhibits the turnover of detergent-isolated enzyme in a similarly slow manner; the progress of this inhibition is halted by palmitate and other fatty acids. The inhibitory bovine serum albumin effect may involve fatty acid depletion from the enzyme. Respiration by cytochrome c oxidase vesicles (proteoliposomes) in the presence of ionophores (uncontrolled) shows only a small inhibition by BSA but preincubation of such vesicles with BSA induces a loss of proton pumping activity. After incubation of BSA-depleted proteoliposomes in the presence of reductant with combinations of fatty acids, pumping activity can be fully restored, suggesting a supportive or even essential role of endogenous fatty acids in H+ translocation by this membranous enzyme.