Observations on the polysaccharide complex present in serum proteins and on the effect of pepsin on serum protein fractions

Abstract

A simple method is described of preparing the polysaccharide complex present in serum proteins. The proteins are subjected to several digestions with proteolytic enzymes and after each digestion the polysaccharide-rich material is precipitated with acid acetone, non-carbohydrate material being relatively soluble in 80% acetone at pH 1. Pepsin is used for the 1st digestion followed by 2 or 3 digestions with trypsin. The polysaccharide complex is obtained in the form of a white powder and contains some non-carbohydrate constituents but is free from tyrosine and tryptophan. Acetyl hexosamine is present and colorimetric detns. are in agreement with the presence of galactose-mannose-acetylglucosamine. After acid hydrolysis the complex develops reducing powers and the laevo-rotation changes to dextro-rotation. In the case of partially digested proteins the splitting off of aromatic amino acids is demonstrated by means of u.-v. absorption spectra. When subjected for a few mins. to the action of proteolytic enzymes seroglycoid is broken down and yields a fraction corresponding to "serum mucoid." Serum mucoid is probably an artefact formed by the breakdown of seroglycoid either by chemical manipulation or by the action of the proteolytic enzymes present in blood serum.