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Media type:
E-Article
Title:
Glyoxysomal β-oxidation of long-chain fatty acids: completeness of degradation
Contributor:
Kleiter, Anna Elisabeth;
Gerhardt, Bernt
imprint:
Springer-Verlag, 1998
Published in:Planta
Language:
English
ISSN:
0032-0935;
1432-2048
Origination:
Footnote:
Description:
<p>The ability of glyoxysomes from sunflower (Helianthus annuus L.) cotyledons to completely degrade long-chain fatty acids into their constituent acetyl units and the time courses of the appearance of acyl-CoA intermediates during β-oxidation have been studied using 14C-labelled substrates at non-saturating concentrations (1.3 to 1.8 μmol·l-1). [14C]Acetyl-CoA was formed from [18-14C]oleate metabolized at a yield of up to 80%, and from [U-14C]palmitate and [U-14C]linoleate to an extent indicating that a maximum of 80% and 30%, respectively, of the substrate β-oxidized had been degraded beyond the C4-CoA intermediate level. To obtain the latter values, an acetyl-CoA-removing system was required during β-oxidation. Constant re-oxidation of the NADH formed during the β-oxidation did not replace the effect of acetyl-CoA removal. Neither the completeness of the linoleate β-oxidation nor the rate of reaction were influenced by NADPH. Medium- and short-chain acyl-CoA intermediates were predominantly detected during β-oxidation of the long-chain substrates employed. The degradation of these intermediates appeared to be stimulated mainly in the presence of an acetyl-CoA-removing system. The time courses of the appearance of intermediates corresponded to a precursor-product relationship between intermediates of decreasing chain lengths.</p>