Biological activities of the two major components of tunicamycin.

Tunicamycin, an antibiotic that inhibits the transfer of N-acetyglucosamine-1-phosphate from UDP-N-acetylglucosamine to dolichol monophosphate and thereby blocks the formation of protein-carbohydrate linkages of the N-glycosidic type, is not a single compound but a mixture of homologous antibiotics. Two major and eight minor homologs have been identified, all of which possess the ability to inhibit protein glycosylation. The biological activities of the two major components of tunicamycin were investigated and found to differ in their ability to inhibit protein glycosylation and in their effectiveness to inhibit protein synthesis. When completely blocking mannose incorporation into protein, one homolog inhibited protein synthesis by 50% while the other had only a negligible effect. The results demonstrate that differences in biological activity can be discriminated among tunicamycin homologs.