Studies on the oxidation of isobutyrylcarnitine by beef and rat liver mitochondria.
Mitochondria from beef liver oxidize isobutyrylcarnitine at approximately 50% the rate of succinate in the presence of rotenone. However, the oxidation rate of isobutyryl coenzyme A in the presence of l(-)-carnitine is very low and can be negligible in both rat and beef liver mitochondria. The limited stimulation of isobutyryl-CoA oxidation by l(-)-carnitine appears to be due to inhibition of isobutyrylcarnitine translocation rather than lack of formation of isobutyrylcarnitine. This conclusion is supported by the fact that: 1) isobutyrylcarnitine oxidation is inhibited by l(-)-carnitine; 2) some oxidation of isobutyryl-CoA is obtained when a low concentration (50 microM) of l(-)-carnitine is used; and 3) under conditions of high isobutyryl-coenzyme A and l(-)-carnitine concentrations (1 mM), isobutyryl-carnitine is produced in near theoretical amounts by these rat liver mitochondria. Other studies demonstrated that less than 25% of the carnitine isobutyryl transferase activity of beef liver mitochondria and rat liver mitochondria is located on the cytosol side of the acylcoenzyme A barrier of these mitochondria.
D000818:Animals; D002331:Carnitine / Q000031:analogs & derivatives* / Q000378:metabolism; D002417:Cattle; D007700:Kinetics; D008930:Mitochondria, Liver / Q000378:metabolism*; D010084:Oxidation-Reduction; D051381:Rats; D013045:Species Specificity
C020381:isobutyryl-1-carnitine; D002331:Carnitine