| 447666 |
Choi YR, Clarke PR, Bieber LL: Studies on the oxidation of isobutyrylcarnitine by beef and rat liver mitochondria. J Biol Chem. 1979 Jul 10;254(13):5580-3.
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. |
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