PubMed1987
Inhibition of replication of Leishmania donovani promastigotes in axenic culture medium by tunicamycin, an inhibitor of asparagine linked protein glycosylation, depends upon the cell density of the culture at the time of addition of tunicamycin as well as upon the concentration of tunicamycin itself. Parasite multiplication in cultures with initial densities of less than or equal to 1 X 10(6) cells ml-1 and a tunicamycin concentration of 1 microgram ml-1 was limited to 2-3 replications, but this limitation was not observed in cultures with initial densities greater than or equal to 2 X 10(6) cells ml-1. Under conditions in which tunicamycin inhibited parasite growth and protein synthesis by only 15% and 6%, respectively, there was a greater than 90% reduction in the level of secreted acid phosphatase activity in comparison to control cultures. The extracellular acid phosphatase activity remaining in tunicamycin treated cultures was electrophoretically distinct from that found in control cultures. No significant decrease in the amount of [35S]methionine incorporated into acid insoluble products in the supernatant of tunicamycin treated cultures was observed, and a radiolabeled protein with an electrophoretic Mr of 97,000 was immunoprecipitated from this supernatant by an anti extracellular acid phosphatase antiserum. It was concluded that the L. donovani extracellular acid phosphatase, previously shown to be a mannose containing glycoprotein, contains N-linked oligosaccharides which are necessary for maintenance of its catalytic activity, but not its secretion.