PURIFICATION AND PROPERTIES OF BILIARY GLYCOPROTEIN-I (BGP-I) - IMMUNOCHEMICAL RELATIONSHIP TO CARCINOEMBRYONIC ANTIGEN

Normal human bile contained a biliary glycoprotein (BGPI), which was immunologically crossreactive with carcinoembryonic antigen (CEA). BGP I was purified by perchloric acid precipitation (1 M), ion exchange chromotography, concanavalin A-Sepharose affinity chromatography and gelfiltration. Purified BGP I had a mol. wt of ~ 90,000 (SDS-PAGE and gelfiltration in 6 M guanidine-HCl) and contained about 40% carbohydrate. The same sugars and amino acids in similar molar proportions as in CEA were detected. The immunological cross-reactivity between BGP I, CEA and 'non-specific crossreacting antigen' (NCA) was established by immunodiffusion and immunoadsorbent experiments using antisera against the three antigens. BGP I differed from CEA and NCA in that it occured in normal human bile and that it contained unique antigenic determinants not present in CEA or NCA. Furthermore, most BGP I preparations lacked methionine in analogy with CEA but in contrast to NCA. A second CEA cross-reactive biliary glycoprotein of lower apparent mol. wt (~ 60,000, SDS-PAGE), termed BGP Ilow was also discovered in human bile. It was present in lower concentrations than BGP I. BGP Ilow was precipitated with BGP I antisera. It has not been established whether it is a degradation product of BGP I or still another member of the CEA glycoprotein family. © 1979.