title: ATP-dependent transport of bile acid intermediates across rat liver peroxisomal membranes.
abstract: The bile acid intermediate 3alpha,7alpha,12alpha-trihydroxy-5beta-cholestanoic acid (THCA) is converted to cholic acid exclusively in peroxisomes by the oxidative cleavage of the side chain. To investigate the mechanism by which the biosynthetic intermediates of bile acids are transported into peroxisomes, we incubated THCA or its CoA ester (THC-CoA) with isolated intact rat liver peroxisomes and analyzed their oxidation products, cholic acid and 3alpha,7alpha,12alpha-trihydroxy-5beta-cholest-24-enoic acid. The oxidation of both THCA and THC-CoA was dependent on incubation time and peroxisomal proteins, and was stimulated by ATP. THC-CoA was efficiently oxidized to cholic acid and 3alpha,7alpha,12alpha-trihydroxy-5beta-cholest-24-enoic acid as compared with THCA, suggesting that THC-CoA is the preferred substrate for transport into peroxisomes. The oxidation of THC-CoA was significantly inhibited by sodium azide, verapamile, and N-ethylmaleimide. Furthermore, the stimulatory effect of ATP on the oxidation was not replaced by GTP or AMP. In addition, the ATP-dependent oxidation of THC-CoA was markedly inhibited by pretreatment of peroxisomes with proteinase K when peroxisomal matrix proteins were not degraded. These results suggest that an ATP-dependent transport system for THC-CoA exists on peroxisomal membranes.
authors.affiliation: Division of Medical Chemistry, Programs for Pharmaceutical Sciences, Graduate School of Biomedical Sciences, Hiroshima University, Kasumi, Minami-ku, Hiroshima 734-8551. mune@hiroshima-u.ac.jp
authors.forename: Mizuho
authors.initials: M
authors.lastname: Une
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Iguchi
authors.forename: Tomoko
authors.initials: T
authors.lastname: Sakamoto
authors.forename: Takashi
authors.initials: T
authors.lastname: Tomita
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Masashi
authors.initials: M
authors.lastname: Morita
authors.forename: Tsuneo
authors.initials: T
authors.lastname: Imanaka
mesh_terms: D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D001693:Biological Transport, Active; D002462:Cell Membrane / Q000378:metabolism; D002777:Cholestanols / Q000378:metabolism*; D002793:Cholic Acids / Q000737:chemistry / Q000378:metabolism*; D019286:Endopeptidase K / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015151:Immunoblotting; D008099:Liver / Q000378:metabolism*; D008297:Male; D009711:Nucleotides / Q000494:pharmacology; D010084:Oxidation-Reduction; D020675:Peroxisomes / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
chemical_list: C117410:3alpha,7alpha,12alpha-trihydroxy--5beta-cholestanoic acid coenzyme A thioester; D002777:Cholestanols; D002793:Cholic Acids; D004791:Enzyme Inhibitors; D009711:Nucleotides; D000255:Adenosine Triphosphate; D019286:Endopeptidase K; D000251:Adenosine Triphosphatases