Palmitate decreases proton pumping of liver-type cytochrome c oxidase.
The H+/e- stoichiometry of reconstituted cytochrome c oxidase from bovine kidney, containing subunit VIaL (liver type), is 0.5 under standard conditions but 1.0 on addition of 1% cardiolipin to the lipid mixture (asolectin). Low concentrations of palmitate (half-maximal effect at 0.5 microm), but not laurate, myristate, stearate, oleate, 1-hexadecanol, palmitoyl glycerol and palmitoyl CoA, decreased the H+/e- ratio in the presence of cardiolipin from 1.0 to 0.5, accompanied by an increase of coupled, but not of uncoupled respiration of proteoliposomes. Cardiolipin and palmitate did not influence the H+/e- stoichiometry and respiration of reconstituted cytochrome c oxidase from bovine heart, containing subunit VIaH (heart-type). The H+/e- stoichiometry of the heart enzyme, however, is decreased from 1.0 to 0.5 by 5 mm intraliposomal ATP (instead of 5 mm ADP). It is assumed that palmitate binds to subunit VIaL. The partial uncoupling of proton pumping in cytochrome c oxidase is suggested to participate in mammalian thermogenesis.
Lee
I
I
Fachbereich Chemie, Philipps-Universität, D-35032 Marburg, Germany.
Kadenbach
B
B
D000818:Animals; D002417:Cattle; D003576:Electron Transport Complex IV / Q000378:metabolism*; D007668:Kidney / Q000187:drug effects / Q000201:enzymology; D008099:Liver / Q000201:enzymology*; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology; D010085:Oxidative Phosphorylation; D019308:Palmitic Acid / Q000494:pharmacology*; D017494:Proton Pumps / Q000378:metabolism*
D017494:Proton Pumps; D019308:Palmitic Acid; D003576:Electron Transport Complex IV