Biosynthesis in Vitro of Hexosamine-containing Substances

1. Two distinct hexosamine-containing substances have been obtained from bovine cardiac valvular tissue which was incubated with labelled glucosamine. These were identified as mucopolysaccharides and glycopeptides respectively, both by the elution pattern from a Sephadex G-50 column and by chemical analysis. 2. In the mucopolysaccharide fraction about 80% of both the total hexosamine and total radioactivity were present; the galactosamine/glucosamine ratio of the amounts was about 1.36. 3. The glycopeptide fractions had about 20% of both total hexosamine and total radioactivity; the galactosamine/glucosamine ratio ofamounts was about 0.44. In this fraction, over 15% of radioactivity was present in sialic acid. 4. In contrast with the concentrations of the several chemical components, there were remarkable differences in the biosynthetic activities among the four valves; the tricuspid valve had highest specific radioactivity in all components of both substances, followed then in turn by mitral, aortic and pulmonary valves. 5. Glucosamine in mucopolysaccharides had a rapid rate of turnover, followed then in turn by turnover rates of both glucosamine and galactosamine in glycopeptides, and of galactosamine in mucopolysaccharides. The possible significance of these findings is discussed.