Phytanoyl-CoA ligase activity in rat liver

The enzymatic activation of phytanic acid to phytanoyl-CoA by rat liver preparations was studied using [1-14C] phytanic acid. Subcellular fractionation studies indicated that phytanoyl-CoA ligase activity was present in both mitochondrial and microsomal fractions. The enzyme activity required ATP, Mg2+, and CoA in addition to phytanic acid. The activity was ATP specific. Among the various tissues examined, the highest activity was in rat liver followed by heart and kidney. The specific activity was, however, high in liver and adipose tissue. The ligase activity was inhibited by AMP, N-ethylmaleimide and iodoacetic acid. At 10 microM concentration, palmitate or stearate did not inhibit the activity. The kinetics of heat inactivation of phytanoyl-CoA ligase (in the presence of unlabeled palmitate) and palmitoyl-CoA ligase yielded a T1/2 of 3-5 min for the former and 25-35 min for the latter suggesting that phytanoyl-CoA ligase may be different from long chain acyl-CoA ligase.