Changes in chemical composition of anterior lens capsules of cataractous human eyes as a function of age

Abstract

Amino acids and carbohydrates were found to account for 80% and 11%, respectively, of the dry weight of the anterior lens capsule of the cataractous human lens. The human lens capsule was found to contain substantial amounts of glycine, hydroxyproline, proline and glycosylated hydroxylysine, as is typical of basement membranes. The monosaccharides present in the lens capsule were identified as glucose, galactose, fucose, mannose, glucosamine, galactosamine and sialic acid. In contrast with basement membranes studied so far, hydroxylysine in human anterior lens capsules from cataractous lenses is almost completely glycosylated. Lenses used in this study were divided into two age groups: ≤ 65 years and &> 65 years. There were statistically significant differences between capsules from the two groups. In the older group, amounts of tyrosine, phenylalanine, histidine, lysine, and arginine were significantly higher and hydroxyproline was significantly lower. These compositional differences are consistent with a smaller proportion of collagen in the older age group.