The carbohydrate complex of the serum proteins

Abstract

The carbohydrate present in serum proteins from horse and ox blood was isolated by hydrolyzing the proteins with 10% Ba(OH)2 for 30-36 hrs., removing the Ba with H2SO4 and precipitating the carbohydrate with basic lead acetate followed by saturation of the solution with baryta. The lead-carbohydrate precipitate was decomposed with acetic acid and re-precipitated and re-liberated several times. Nitrogenous impurities were removed with Hopkins'' reagent (10% HgSO4 in 3% H2SO4) and after removing Pb, Hg, and H2SO4 the neutral solution of the carbohydrate was evaporated to a syrup and the carbo-hydrate precipitated with an alcohol-ether mixture, as a hygroscopic creamy white powder. Solutions are optically inactive and do not reduce Fehling''s solution until after hydrolysis. The compound proved to be an amino-trisaccharide, glucosamino-dimannose, in which the -NH2 group was free. Serum globulin contains about 3.7% of this carbohydrate. Apparently the same compound is present in the proteins of egg white.