title: On reagents that convert cytochrome oxidase from an inactive to an active coupling state.
abstract: Cytochrome oxidase (ferrocytochrome c:oxygen oxidoreductase, EC 1.9.3.1) of beef heart mitochondria, prepared by a standard method and brought to the highest purity level, is essentially inactive when tested in the aerobic assay involving oxidation of reduced cytochrome c by molecular oxygen. Three reagents (lysolecithin, Tween 20, and exogenous phospholipids) can convert cytochrome oxidase from an inactive to an active coupling state. These conversions are reversible: i.e., removal of the inducing agent leads to loss of activity. The evidence for the intrinsic coupling capability is that cytochrome oxidase in the active state invariably generates a proton gradient during respiration, and such gradient formation is demonstrable even when cytochrome oxidase is not inserted into a liposome.
mesh_terms: D000818:Animals; D002417:Cattle; D003576:Electron Transport Complex IV / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D008244:Lysophosphatidylcholines / Q000494:pharmacology; D008564:Membrane Potentials; D008929:Mitochondria, Heart / Q000378:metabolism; D010101:Oxygen Consumption; D010743:Phospholipids / Q000494:pharmacology; D011136:Polysorbates / Q000494:pharmacology; D011522:Protons
chemical_list: D008244:Lysophosphatidylcholines; D010743:Phospholipids; D011136:Polysorbates; D011522:Protons; D003576:Electron Transport Complex IV