Production of acyl-carnitines from the metabolism of [U-14C]3-methyl-2-oxopentanoate by rat liver and skeletal muscle mitochondria.
A sensitive method of continuous on-line radio-high performance liquid chromatography (HPLC) was used to detect the specific radio-labelled acyl-carnitine esters derived from the oxidation of [U-14C]3-methyl-2-oxopentanoate by rat liver and muscle mitochondrial fractions. The recoveries of carnitine, acetyl-carnitine, propionyl-carnitine, 2-methylbutyryl-carnitine, and hexanoyl-carnitine were 98.7% (+/- 5.4; SEM, n = 3), 91.4% (+/- 7.6), 89.4% (+/- 5.2), 84.6% (+/- 6.8), and 87.9% (+/- 7.8), respectively, from quenched mitochondrial incubations. This method demonstrated that rat liver and muscle mitochondria generate acetyl-carnitine, propionyl-carnitine and 2-methylbutyryl-carnitine when incubated with [U-14C]3-methyl-2-oxopentanoate in the presence of carnitine. The production of acetyl-carnitine was almost similar in the 2 tissues. Muscle mitochondria produced higher amounts of propionyl-carnitine and 2-methylbutyryl-carnitine than liver mitochondria. These observations suggest a limited utilization of propionyl-CoA by muscle mitochondria which, through a mechanism of feed-back inhibition, may have contributed to the accumulation of 2-methylbutyryl-CoA. This study provides further evidence for the importance of carnitine in the modulation of the mitochondrial [acyl-CoA/[CoA] pool.
Bhuiyan
A K
AK
Department of Child Health, Medical School, University of Newcastle Upon Tyne, U.K.
Seccombe
D
D
Bartlett
K
K
D000108:Acetylcarnitine / Q000378:metabolism; D000597:Amino Acids, Branched-Chain / Q000378:metabolism; D000818:Animals; D002331:Carnitine / Q000031:analogs & derivatives* / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D007651:Keto Acids / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008930:Mitochondria, Liver / Q000378:metabolism*; D008931:Mitochondria, Muscle / Q000378:metabolism*; D010084:Oxidation-Reduction; D051381:Rats; D017208:Rats, Wistar
D000597:Amino Acids, Branched-Chain; D007651:Keto Acids; C016211:alpha-keto-beta-methylvaleric acid; C061301:hexanoylcarnitine; C003223:propionylcarnitine; D000108:Acetylcarnitine; D002331:Carnitine