Intramitochondrial control of the oxidation of hexadecanoate in skeletal muscle. A study of the acyl-CoA esters which accumulate during rat skeletal-muscle mitochondrial beta-oxidation of [U-14C]hexadecanoate and [U-14C]hexadecanoyl-carnitine.
1. We describe the acyl-CoA and acyl-carnitine esters which arise from the incubation of well-coupled State 3 rat skeletal-muscle mitochondrial fractions with [U-14C]hexadecanoate and [U-14C]hexadecanoyl-carnitine. 2. Acyl-CoA ester intermediates of chain length 16, 14, 12, 10 and 8 carbons were detected. 3. Although incubations were in steady state in respect of oxygen consumption, 14CO2 production and generation of acid-soluble radioactivity, quantitative analysis of acyl-CoA esters showed that steady state was not achieved in respect of all intermediates. 4. 3-Hydroxyacyl- and 2-enoyl-CoA and -carnitine esters were found under normoxic conditions. 5. Direct measurement of NAD+ and NADH shows that under identical incubation conditions our observations cannot be explained by gross perturbation of the [NAD+]/[NADH] ratio. 6. We hypothesize that there is a small pool of rapidly recycling NAD+ channelled between complex I of the respiratory chain and the newly described mitochondrial-inner-membrane-associated beta-oxidation trifunctional enzyme [Uchida, Izai, Orii and Hashimoto (1992) J. Biol. Chem. 267, 1034-1041].
Eaton
S
S
Departments of Child Health, Medical School, University of Newcastle upon Tyne, U.K.
Bhuiyan
A K
AK
Kler
R S
RS
Turnbull
D M
DM
Bartlett
K
K
D000214:Acyl Coenzyme A / Q000378:metabolism*; D000818:Animals; D004952:Esters / Q000378:metabolism; D007425:Intracellular Membranes / Q000378:metabolism; D008297:Male; D008931:Mitochondria, Muscle / Q000378:metabolism*; D009132:Muscles / Q000378:metabolism*; D009243:NAD / Q000378:metabolism; D010084:Oxidation-Reduction; D010169:Palmitic Acids / Q000378:metabolism*; D010172:Palmitoylcarnitine / Q000378:metabolism*; D011048:Polarography; D051381:Rats; D017208:Rats, Wistar
D000214:Acyl Coenzyme A; D004952:Esters; D010169:Palmitic Acids; D009243:NAD; D010172:Palmitoylcarnitine