Lithocholic acid in human liver: Identification of ∈‐lithocholyl lysine in tissue protein

Abstract

Human liver had been shown to contain two forms of lithocholic acid. One form is extractable by 95% ethanol‐ammonia, 1000∶1, v/v (soluble lithocholate, SL) and the other form is firmly bound to the tissue residue. The latter, tissue‐bound lithocholic acid (TBL), can be enzymatically released by means of the specific clostridial peptide bond hydrolase, cholylglycine hydrolase (cholanoyl amino acid hydrolase, EC no. 3.5). Solvolytic procedures for the analysis of hepatic lithocholic acid sulfate revealed that almost all of the TBL was non sulfated, while in the SL fraction there was an apparent preponderance of the sulfated form. Cholylglycine hydrolase liberates free labeled lithocholic acid from synthetic [24‐14C] lithocholyl‐bovine serum albumin and from [24‐14C]lithocholyl polylysine. By analogy, the enzyme releases lithocholic acid from tissue protein in which the bile acid is conjugated through amino groups of basic side chains. Hydrolysis of [24‐14C] lithocholyl polylysine with 6n HC1 yielded ∈‐[24‐14C] lithocholyl lysine, which was chromatographically similar to the product obtained by acid hydrolysis of TBL. Chromatographic, infrared, and mass spectroscopic studies with synthetic N‐α‐lithocholyl lysine, N‐∈‐lithocholyl lysine, and N‐α‐∈‐Bis lithocholyl lysine showed the hydrolytic product from TBL to be N‐∈‐lithocholyl lysine. Since monohydroxy bile acids, such as lithocholic acid, are known to show unusual cytotoxic properties, the identification of TBL in human liver poses important questions regarding the role of lithocholate in liver injury.

Production of a Monoclonal Antibody for Sensitive Monitoring of Deoxycholic Acid Residues Anchored on Endogenous Proteins

“…Indeed, it has been exhibited that LCA binds to lysine residues of histone in colonic mucosa epithelial cells, resulting in denaturation of the DNA double strand. 2 The monoclonal antibody Ab#88 established in this study would be a useful tool for examining the utility of the tissue-bound DCA or liberated DCA-Lys molecules as a diagnostic marker of the cancer. Examination of the DCA residues on various tissue slices and cells is now ongoing in our laboratories, as well as generation of monoclonal antibodies against the CA and CDCA residues.…”

Exploratory metabolomics study of the experimental opisthorchiasis in a laboratory animal model (golden hamster, Mesocricetus auratus)

“…A similar transient pattern to the bile acids was also observed for the spectral areas where resonate lysine and a product of its catabolism 5-aminopentanoic acid are located. Despite an intriguing similarity, a “simple” interpretation where lysine would be considered as a breakdown product of the conjugated bile acids is difficult to accept; the lysine conjugates are rather unusual and were reported only as the minor products of lithocholic acid in the liver [ 30 ]. Another group of the metabolites which are related to the physiological control of the lipid metabolism consist of nicotinic acid and its metabolites nicotinuric acid and nicotinamide-N-oxide.…”

Production and Characterization of a Monoclonal Antibody to Capture Proteins Tagged with Lithocholic Acid

“…In 1977, lithocholic acid (LCA), a hydrophobic bile acid, was firstly isolated as a tissue-bound form from pathological specimens of human livers by Nair et al, 1,2 and its concentration was reported to be elevated in the livers of rat treated with a carcinogen, methylazoxymethanol. 3 Furthermore, the tissuebound LCA was detected in normal and neoplastic human mammary tissues and in the neoplasms of the uterus, kidney, lung and the colon.…”