Miguel Contreras

72 Topographical localization of Peroxisomal Acyl-CoA Ligases: Differential localization of Palmitoyl-CoA and Lignoceroyl-CoA Ligases

We found that peroxisomal licjnoceroyl-CoA ligase, like palmitoyl-CoA ligase, is present in the peroxisomal membrane. To further define the role of peroxisomal acyl-CoA ligases we examined the transverse topographical localization of enzymatic sites of palmitoyl-CoA and lignoceroyl-CoA ligases in the peroxisomal membranes. Proteolytic enzyme treatment irihibited palmitoyl-CoA ligase activity in intact peroxisomes and ligrraceroyl-CoA ligase activity was inhibited only if peroxisomes were disrupted prior to trypsin treatment. Antibodies to palmitoyl-CoA ligase and to peroxisomal membrane proteins (PMP) inhibited palmtoyl-CoA ligase in intact peroxisomes, and no pool of “latent” activity appeared when antibody-treated peroxisomes were disrupted. 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 ligncceroyl-CoA ligase is on the luminal surface of peroxisomal membranes. The implication of these findings to X-adrenoleukodystiuphy will be discussed.

KUPFFER CELLS MODULATE THE LIPOPOLYSACCHARIDE-INDUCED LIPID ALTERATIONS IN RAT LIVER PEROXISOMES. 610

KUPFFER CELLS MODULATE THE LIPOPOLYSACCHARIDE-INDUCED LIPID ALTERATIONS IN RAT LIVER PEROXISOMES. 610

73 Rhizomelic Chondrodysplasia Punctata: Metabolic Studies in Isolated Peroxisomes

The Rhizomelic form of chondrodysplasia puntata (RCDP) is a fatal autosomal recessive peroxisomal disorders. Clinically, it is characterized by abnormal calcification of extremities, dwarfism, cataracts, skin charges and severe mental retardation. The biochemical findings were abnormal activities dihydroxyacetonephosphata acyltransferase (DHAP-AT) oxidation of phytanic acid whereas oxidation of lignoceric acid was normal.Peroxisomes isolated from two cell lines of RCDP and control each were compared for biochemical studies. The RCDP peroxisomes had the same density (1.178 gm/ml) as control peroxisomes. The residual activity (0.5% of control) of DHAP-AT was observed only in the peroxiscmes from RCDP and no such activity was observed in any other region of the gradient. The rates of activation and, oxidation of lignoceric acid was normal in peroxisomes from RCDP. The peroxisomes from RCDP contained 3-ketoacyl-CoA thiolase in the unprocessed form (44 KDa) whereas peroxisomes from normal peroxisomes contained both unprocessed (44KDa) and mature (41 KDa) forms. These results suggest that processing of 3-ketoacyl-CoA thiolase takes place in peroxisomes and recognition signals for its transport into peroxisomes were normal in RCDP.