Bile acids in tissues: binding of lithocholic acid to protein.
Human liver contains two forms of lithocholic acid. One form is readily extractable by 95% ethanol/0.1% ammonia (soluble lithocholate, SL), while the other remains firmly bound to the residue (tissue-bound lithocholate, TBL). TBL could be hydrolytically released using clostridial cholanoylamino acid hydrolase, suggesting a peptide link between lithocholate and protein. With bovine serum albumin (BSA), lithocholic acid showed spontaneous amino group-modifying activity. When small molecular weight lysine (alpha-t-BOC-1-lysyl-beta-naphthylamide) and arginine peptides (alpha-CBZ-di-arginyl-beta-naphthylamide) were used in place of BSA, lithocholate bound specifically to the lysine peptide. The unusual affinity for lysine suggested that this amino acid might be involved as a residue in TBL. Synthesis of lithocholyl lysines and comparison with products of acid hydrolysis of TBL established epsilon-lithocholyl lysine as the predominant form in which lithocholic acid is found in tissue bound form.
D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D001647:Bile Acids and Salts / Q000032:analysis; D002417:Cattle; D006801:Humans; D008095:Lithocholic Acid / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D008103:Liver Cirrhosis / Q000378:metabolism; D008239:Lysine / Q000378:metabolism; D011485:Protein Binding; D012710:Serum Albumin, Bovine / Q000378:metabolism; D012997:Solvents; D014018:Tissue Distribution
D000596:Amino Acids; D001647:Bile Acids and Salts; D012997:Solvents; D012710:Serum Albumin, Bovine; D008095:Lithocholic Acid; D008239:Lysine