Studies on the sugar fractions of the insoluble fibrous network of the corneal stroma

Abstract

Calf corneas were extracted with a buffer containing M CaCl2, 0.05 M Tris and 0.02 M citric acid, at pH 7.5. The residual stroma was digested successively by collagenase and pronase. The glycopeptides obtained were separated by gel filtration and high voltage electrophoresis. The sugar and amino acid content of the isolated glycopeptides was determined. Two types of sugar chains were detected: (a) chains with a more complicated structure, containing galactose, glucose, mannose and glucosamine; (b) disaccharidic and monosaccharidic side chains containing galactose and glucose or galactose alone and linked O‐glycosidically to the OH groups of hydroxylysine. The Hyl‐Gal‐Glc compound was isolated and identified with the compound isolated by Butler and Cunningham from calf skin collagen, by the study of its composition, thin layer chromatography and high voltage electrophoresis.The stroma of the calf cornea contains about 4 times more hexoses in the small glycopeptides of type b (di‐ and monosaccharides) than in the higher molecular weight mannose‐containing chains.