Catabolism of Fatty Acids (a- and ß-Oxidation)

Catabolism of fatty acids — in the strict sense of the term — occurs by the oxidative process known as ß-oxidation. It proceeds by oxidation in the ß-position of the fatty acid carbon chain to the carboxyl group and sequential removal of C₂ units (acetyl-CoA). Prior to degradation by ß-oxidation, fatty acids have to be activated to an acyl-coenzyme A (CoA). Two mechanisms by which fatty acids are activated in higher plant peroxisomes are known: activation by acyl-CoA synthetase and activation by oxidative decarboxylation. The ß-oxidation reaction sequence starts by oxidation of acyl- CoA to 2-trans-enoyl-CoA. Catabolism of straight-chain, saturated, common fatty acids is accomplished by the ß-oxidation pathway. Catabolism of physiologically relevant fatty acids possessing other molecular structures is, in general, more complex. Double bonds of naturally occurring unsaturated fatty acids are in the cis configuration which forms a barrier to continuous ß- oxidation.