AUTHOR:
Lennart Roden, Chemisty Dept. II, Karolinska Institutet, Stockholm, Sweden;
PUBLISHED:
Arkiv for Kemi Band 10 nr 23 (1956)
In the biosynthesis of hyaluronic acid in streptococci, glutamine is known to participate as a nitrogen donor for glucosamine formation. A similar function of glutamine in the synthesis of mammalian mucopolysaccharides was indicated by our studies on the formation of chondroitin sulphuric acid in slices of cartilage. Glutamine was found to be a rate-limiting substrate for the synthesis of mucopolysaccharide in this system, and an increased uptake of isotopic precursors took place when it was added to the medium. Since glutamine was most likely involved in the hexosamine synthesis, it seemed pertinent to investigate the influence of hexosamines on the formation of chondroitin sulphuric acid in the aforementioned in vitro system. The present paper describes the effects of glucosamine and galactosamine on the incorporation of S35-labelled sulphate and uniformly labelled C14-glucose into chondroitin sulphuric acid in slices of cartilage. The following observations were made:
- The incorporation of S35-labelled sulphate in chondroitin sulphuric acid was enhanced by glucosamine to a maximum of about 3 times the control value. At high concentrations, the increase was smaller and approached the control value.
- Galactosamine increased the S35 to maximally twice the control value in a concentration 100 times larger thjan the glucosamine concentration which gave the same stimulation.
- The maximal stimulation of S35 uptake by glucosamine could not be further increased by the addition of glutamine.
- The stimulation of S35 uptake by glucosamine was almost completely abolished by glucose in physiologic concentrations.
- The incorporation of C14-labelled glucose into chondroitin sulphuric acid was increased at a low concentration of glucosamine and decreased at a high concentration in comparison with controls without glucosamine added. The label of the uronic acid was increased at low glucosamine concentration and decreased at the high concentration. The galactosamine moiety of chondroitin sulphuric acid had a decreased label in both cases.
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