Modulation of cytochrome oxidase activity by inorganic and organic phosphate.
The activity of cytochrome oxidase reconstituted into phospholipid vesicles has been studied as a function of orthophosphate, ATP and inositol hexakisphosphate concentrations. The respiratory-control ratio was found to be quite sensitive to these compounds and was inversely related to the anion concentration. This effect is related to a phosphate-dependent decrease in the rate constant for ferrocytochrome c oxidation observed in the presence of ionophores. The data cannot be interpreted simply on the basis of ionic strength, which is known to limit cytochrome c binding to cytochrome oxidase, since cytochrome oxidase-containing vesicles responded differently to phosphate depending on the energization state of the phospholipid membrane.
Malatesta
F
F
Department of Experimental Medicine and Biochemical Sciences, University of Rome Tor Vergata, Italy.
Antonini
G
G
Sarti
P
P
Brunori
M
M
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D003576:Electron Transport Complex IV / Q000037:antagonists & inhibitors / Q000378:metabolism*; D007476:Ionophores / Q000494:pharmacology; D007700:Kinetics; D010084:Oxidation-Reduction; D010710:Phosphates / Q000494:pharmacology*; D010833:Phytic Acid / Q000494:pharmacology*
D007476:Ionophores; D010710:Phosphates; D010833:Phytic Acid; D000255:Adenosine Triphosphate; D003576:Electron Transport Complex IV