Topographical localization of peroxisomal acyl-CoA ligases: differential localization of palmitoyl-CoA and lignoceroyl-CoA ligases

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Abstract
We found that peroxisomal lignoceroyl-CoA ligase, like palmitoyl-CoA ligase, is present in the peroxisomal membrane whereas the peroxisomal .beta.-oxidation enzyme system is localized in the matrix. To further define the role of peroxisomal acyl-CoA ligases (membrane component) in providing acyl-CoA for peroxisomal .beta.-oxidation, we examined the transverse topographical localization of enzymatic sites of palmitoyl-CoA and lignoceroyl-CoA ligases in the peroxisomal membranes. The disruption of peroxisomes by various techniques resulted in the release of a "latent" pool of lignoceroyl-CoA ligase activity while palmitoyl-CoA ligase activity remained the same. Proteolytic enzyme treatment inhibited palmitoyl-CoA ligase activity in intact peroxisomes but had no effect on lignoceroyl-CoA ligase activity. Lignoceroyl-CoA ligase activity was inhibited only if peroxisomes were disrupted with detergent before trypsin treatment. Antibodies to palmitoyl-CoA ligase and to peroxisomal membrane proteins (PMP) inhibited palmitoyl-CoA ligase in intact peroxisomes, and no pool of "latent" activity appeared when antibody-treated peroxisomes were disrupted with detergent. On the other hand, disruption of PMP antibody-treated peroxisomes with detergent resulted in the appearance of a "latent" pool of lignoceroyl-CoA ligase activity. These results demonstrate that the enzymatic site of palmitoyl-CoA ligase is on the cytoplasmic surface whereas that for lignoceroyl-CoA ligase is on the luminal surface of peroxisomal membranes. This implies that palmitoyl-CoA is synthesized on the cytoplasmic surface and is then transferred to the matrix through the peroxisomal membrane for .beta.-oxidation in the matrix. Lignoceric acid, on the other hand, is first transported through the peroxisomal membrane as such and is then activated to lignoceroyl-CoA on the luminal surface of the membrane before it is oxidized by the .beta.-oxidation system in the matrix, and implication of these findings are discussed for X-linked adrenoleukodystrophy, a disorder with deficient activity of peroxisomal lignoceroyl-CoA ligase.