Chondroitin sulfate glycosyltransferases in cultured chondrocytes. Turnover, oscillatory change during growth, and suppression by 5-bromodeoxyuridine.

Activity levels of three glycosyltransferases (UDP-D-xylose:core protein xylosyltransferase, UDP-D-galactose:D-xylose galactosyltransferase, and UDP-N-acetyl-D-galactosamine: (GluUA-GalNAc-4-sulfate)3 N-acetylgalactosaminyltransferase), which are involved in the biosynthesis of chondroitin sulfate, were measured during the development of chrondrocytes in monolayer culture. Maxima in enzyme specific activities occurred on Day 8 of culture and preceded the maximum rate of synthesis of chondroitin sulfate proteoglycan (Day 10) by 2 days. The activity of xylosyltransferase was lowered by treatment of cells with inhibitors of RNA and protein synthesis, whereas the activities of the other two glycosyltransferases were relatively stable to treatments with these drugs. In the presence of puromycin, xylosyltransferase decayed with a half-life of 2 to 3 hours in rapidly growing cells, while galactosyltransferase decayed with a half-life or approximately 12 hours, indicating that the chrondroitin sulfate glycosyltransferases are not coordinately synthesized and degraded. 5-Bromo-2'-deoxyuridine also caused a greater decrease in xylosyltransferase activity than in the activities of the other two glycosyltransferases. The differential effect of 5-bromo-2'-deoxyuridine on glycosyltransferase activity was also showm by correlating the residual enzyme activity with the potential for synthesis of chrondroitin sulfate chains as measured in the presence of beta-xylosides.