Abstract
The nature of the mucopolysaccharide of the cornea has been much debated. A number of investigators have considered it to be a mucoitin sulfuric acid, 1 while others have found no sulfuric acid. 2 It was reported recently, on the basis of colorimetric analysis, 3 that the carbohydrate contained an amino sugar and sulfuric acid, but galactose instead of uronic acid. Most of the reports have been based on analyses of protein complexes (“mucoids”) or of digests prepared by strong alkali.
In the past we have prepared this mucopolysaccharide acid in high yields both by alkaline digestion and by more gentle methods which avoid the use of strong alkali. 4 Our preparations contained one mol each of hexosamine, acetyl, uronic acid, and sulfuric acid, and had the same composition and general properties as those of the mucoitin-sulfuric acid obtained from gastric mucosa. 5 Good yields of glucos-amine were isolated from both acids. In several important respects, however, the two compounds were found to differ: (1) the acid of cornea always formed quite viscous aqueous solutions, while that of gastric mucosa did not; (2) the specific rotation of the acid from cornea was about −50°, while that of the gastric mucosa was around 0 (+2° to −8°); and (3) the acid from gastric mucosa was completely refractory to the specific enzyme from pneumococcus, 6 while the polysaccharide from cornea was hydrolyzed by this enzyme at about half the rate of hyaluronic acid. From this latter finding and from the fact that the rotation of hyaluronic acid is similar to that of the cornea polysaccharide, we conclude that cornea polysaccharide is the naturally-occurring mono-sulfuric acid ester of hyaluronic acid.
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