Intermediates of peroxisomal beta-oxidation. A study of the fatty acyl-CoA esters which accumulate during peroxisomal beta-oxidation of [U-14C]hexadecanoate.
1. 14C-labelled fatty acyl-CoA esters resulting from beta-oxidation of [U-14C]hexadecanoate by peroxisomal fractions isolated from rats treated with clofibrate showed the presence of the full range of saturated intermediates down to acetyl-CoA. 2. The pattern of intermediates generated was fairly constant. At low concentrations of [U-14C]hexadecanoate (50 microM), decanoyl-CoA was present in lowest amounts. At higher concentrations of [U-14C]hexadecanoate (greater than 100 microM), all intermediates of chain length shorter than 12 carbon atoms (except acetyl-CoA) were present at similar low concentrations; the process of beta-oxidation now resembling chain-shortening of hexadecanoate by two cycles of beta-oxidation. 3. In the absence of an NAD(+)-regenerating system [pyruvate and lactate dehydrogenase (EC 1.1.1.28)] 2-enoyl- and 3-hydroxyacyl-CoA esters were generated, suggesting that re-oxidation of NADH is essential for optimal rates of peroxisomal beta-oxidation in vitro. 4. At high concentrations of [U-14C]hexadecanoate (greater than 100 microM), 3-oxohexadecanoyl-CoA was produced, suggesting that thiolase (acetyl-CoA acetyltransferase; EC 2.3.1.9) can become rate-limiting for peroxisomal beta-oxidation.
Department of Child Health, Medical School, University of Newcastle upon Tyne, U.K.
K
K
Bartlett
R
R
Hovik
S
S
Eaton
N J
NJ
Watmough
H
H
Osmundsen
D000214:Acyl Coenzyme A / Q000378:metabolism; D000818:Animals; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D008297:Male; D008830:Microbodies / Q000378:metabolism*; D010084:Oxidation-Reduction; D010169:Palmitic Acids / Q000378:metabolism*; D011773:Pyruvates / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains
D000214:Acyl Coenzyme A; D010169:Palmitic Acids; D011773:Pyruvates; D007770:L-Lactate Dehydrogenase