The effects of temperature and some inhibitors on the carnitine exchange system of heart mitochondria.
1. 11-Trimethylamino-undecanoyl-L-carnitine (Ki = 56 muM) and 6-trimethylaminohexanoyl-L-carnitine (Ki = 1.3 mM) are competitive inhibitors of the ox heart mitochondrial carnitine exchange system. The latter is itself a poor substrate, with a V about 0.7% of that for carnitine. These compounds have been used as 'stop inhibitors' in a study of the effect of temperature on the carnitine exchange. 2. The carnitineout in equilibrium carnitinein exchange has a temperature coefficient (Q10) of 8.5 and an activation energy of 176 kJ/mol which is constant from 0 degrees - 18 degrees C. The Km for L-carnitine (5.3 mM) is also constant over this temperature range. 3. The slow efflux (leak) of mitochondrial L-[14C]carnitine in the absence of external substrate has a similar temperature dependence and is also inhibited by 11-trimethylamino-undecanoyl-L-carnitine. It is probably mediated by the same system as the very much faster exchange with external carnitine.
D000818:Animals; D001667:Binding, Competitive; D001693:Biological Transport, Active; D002151:Calorimetry; D002331:Carnitine / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology; D002417:Cattle; D007700:Kinetics; D008931:Mitochondria, Muscle / Q000187:drug effects / Q000378:metabolism*; D008954:Models, Biological; D009206:Myocardium; D013696:Temperature
C013722:6-trimethylaminohexanoyl-L-carnitine; D002331:Carnitine