Effect of the #alpha#-Glucosidase Inhibitor, Bromoconduritol, on Carobhydrate Metabolism in the Silverleaf Whitefly, Bemisia argentifolli

摘要

The involvement of a-glucosidase in the partitioning of ingested sucrose between excretion and incorporation was investigated , in the silverleaf whitefly {Bemisia argentifolii}. Approximately half of the a-glucosidase activity in adult whiteflies was soluble and the remainder was associated with membranes. In contrast, almost all of the trehalulose synthase was membrane-associated. Isoelectric focusing revealed that soluble and membrane-asso- ciated a-glucosidases were each composed of several isozymes in the pH 5 to 6.5 range, but the distribution of activity among the various isozymes was different. Bromoconduritol, an inhibi- tor of glucosidases, inhibited trehalulose synthase and a-glucosi- dase activities in whitefly extracts. Inhibition was greatest when bromoconduritol was incubated with extracts prior to the addi- tion of sucrose, consistent with the irreversible nature of this inhibitor. Addition of bromoconduritol to artificial diets de- creased the extractable trehalulose synthase and a-glucosidase activities by about 30 and 50%, respectively. Ingestion of bromoconduritol reduced the amount of carbohydrate excreted by about 80% without changing the distribution of the major honeydew sugars or causing an increase in the proportion of sucrose that was excreted. Ingestion of bromoconduritol did not affect respiration, the content and distribution of soluble car- bohydrates in whitefly bodies, or the conversion of labeled su- crose into glucose, trehalose and isobemisiose. The results indicate that partitioning of ingested carbon between excretion and metabolism in whiteflies is highly regulated, probably in- volving multiple forms of a-glucosidase that facilitate a separa- tion of the processes involved in the metabolic utilization of sucrose from those involved in excretion of excess carbohydrate. Arch. Insect Biochem. Physiol. 45:117-128, 2000. Published 2001 Wiley-Liss, Inc.