Factors which can influence beta-oxidation by peroxisomes isolated from livers of clofibrate treated rats. Some properties of peroxisomal fractions isolated in a self-generated Percoll gradient by vertical rotor centrifugation.

1. Oxidation of radioactivity labeled acyl-CoA esters by apparently intact peroxisomes, isolated from rats treated with clofibrate, was stimulated by about 100% by added oxaloacetate. Added pyruvate gave much smaller stimulation. This stimulation is proposed to be due to re-oxidation of NADH generated during peroxisomal beta-oxidation of acyl-CoA esters. 2. Additions of these alpha-ketoacids, and of CoA, were found to influence extent of peroxisomal beta-oxidation of [U-14C]palmitoyl-CoA. Various concentrations of added CoA was markedly less inhibitory to oxidation of [14-14C]erucoyl-CoA and [10-14C]elaidoyl-CoA, as compared to [U-14C]palmitoyl-CoA. 3. Added NADP+, at concentrations higher than 0.5 mM, added NADPH and NADH were inhibitory to peroxisomal beta-oxidation of [U-14C]palmitoyl-CoA. Significant inhibition was found at concentrations which were too high for this to be of significance in vivo.