Accumulation of medium chain Acyl-CoAs during beta-oxidation of long chainfatty acid by isolated peroxisomes from rat liver

We have reported fatty alcohol synthesis accompanied by chain elongation in liver peroxisomes (Biochim. Biophys. Acta, 1346, 38 (1997)). In the presen t experiment, we studied what kind of acyl-CoA(s) destined to be utilized a s primer for fatty alcohol synthesis accumulate(s) during peroxisomal beta -oxidation. Peroxisomes were prepared from rat liver treated with clofibrat e, a peroxisome proliferator, and incubated with [U-C-14]palmitate, in orde r to investigate acyl-CoAs after beta -oxidation. At 1 mM concentration, Mg ATP activated beta -oxidation, but inhibited beta -oxidation at concentrati ons higher than 1 mM. After incubation of peroxisomes with palmitate, vario us acyl-CoAs were formed. Among medium-chain labelled acyl-CoAs, octanoyl-C oA was mainly detected. These results suggest that octanoyl-CoA accumulates during beta -oxidation of palmitate. When peroxisomes were incubated with [9,10-H-3]palmitate and [9,10-H-3]stearate, among medium-chain acyl-CoAs, o ctanoyl-CoA and decanoyl-CoA were primarily detected, respectively, suggest ing the occurrence of at least 1 cycles of beta -oxidation of both fatty ac ids by peroxisomes.