Accumulation of Medium Chain Acyl-CoAs during β-Oxidation of Long Chain Fatty 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 present experiment, we studied what kind of acyl-CoA(s) destined to be utilized as primer for fatty alcohol synthesis accumulate(s) during peroxisomal β-oxidation. Peroxisomes were prepared from rat liver treated with clofibrate, a peroxisome proliferator, and incubated with [U-14C]palmitate, in order to investigate acyl-CoAs after β-oxidation. At 1 mM concentration, MgATP activated β-oxidation, but inhibited β-oxidation at concentrations higher than 1 mM. After incubation of peroxisomes with palmitate, various acyl-CoAs were formed. Among medium-chain labelled acyl-CoAs, octanoyl-CoA was mainly detected. There results suggest that octanoyl-CoA accumulates during β-oxidation of palmitate. When peroxisomes were incubated with [9,10-3H]palmitate and [9,10-3H]stearate, among medium-chain acyl-CoAs, octanoyl-CoA and decanoyl-CoA were primarily detected, respectively, suggesting the occurrence of at least 4 cycles of β-oxidation of both fatty acids by peroxisomes