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 s hift of the Soret band of bovine cytochrome c oxidase with a slow biph asic 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. Resp iration by cytochrome c oxidase vesicles (proteoliposomes) in the pres ence 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 ac tivity can be fully restored, suggesting a supportive or even essentia l role of endogenous fatty acids in H+ translocation by this membranou s enzyme.