Expression in Xenopus oocytes of rat liver mRNA coding for a bile salt-dependent cholesteryl ester hydrolase.
A catalytically active bile salt-dependent cholesteryl ester hydrolase (CEH) was expressed when Xenopus oocytes were injected with rat liver mRNA. The expressed CEH activity was highly dependent on the presence of trihydroxy bile salts (cholate or one of its conjugates); maximum hydrolytic activity was observed in the presence of 10 mM sodium cholate. The expressed CEH was not activated by dihydroxy bile salts (deoxycholate and its conjugates). In the presence of 10 mM sodium cholate, the CEH activity was maximal near pH 7 but was significant between pH 6 and 8. Monospecific immune IgG raised against rat pancreatic CEH completely inhibited the CEH expressed in Xenopus oocytes. Phenylmethylsulfonyl fluoride, a serine enzyme inhibitor, was inhibitory to the expressed CEH activity, whereas p-chloromercuribenzoate (up to 5 mM), a potent thiol-blocking agent, did not significantly inhibit the expressed activity. These experiments clearly demonstrate that the liver contains an mRNA encoding a bile salt-dependent CEH activity and suggest that the uptake of pancreatic enzyme is not necessarily the source of liver CEH as has been speculated.
Department of Physiology and Biochemistry, Medical College of Pennsylvania, Philadelphia 19129.
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Zolfaghari
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Harrison
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Ross
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EA
Fisher
D000818:Animals; D001647:Bile Acids and Salts / Q000494:pharmacology*; D002265:Carboxylic Ester Hydrolases / Q000235:genetics*; D019826:Cholic Acid; D002793:Cholic Acids / Q000494:pharmacology; D005260:Female; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008845:Microinjections; D009865:Oocytes / Q000201:enzymology*; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics*; D051381:Rats; D002787:Sterol Esterase / Q000235:genetics* / Q000378:metabolism; D014982:Xenopus laevis
D001647:Bile Acids and Salts; D002793:Cholic Acids; D012333:RNA, Messenger; D002265:Carboxylic Ester Hydrolases; D002787:Sterol Esterase; D019826:Cholic Acid