Effect of sucrose feeding on the induction of honeybee haemolymph glucosidase (E.C. 188.8.131.52)
M. Bounias And M. R. J. Morgan
The kinetic properties (i.e maximum velocity Vm, dissociation constant Kh, and Hill coefficient h) of the ex-glucosidase complex of honeybee haemolymph have been studied in adult workers, from emergence to day 16, under continuous feeding with 2-M sucrose, alone or with the addition of 1.6-mM chloramphenicol as an inhibitor of protein synthesis (IPS). In the absence of IPS, Vmgradually increases to reach 40 times the initial value by day 16, with a trough of 8-12 times the initial value at days 9-12. In the presence of IPS, Vmvalues are consistently depressed by a factor increasing from 1.2 at day 2 to 3.6 at day 16. The constant Kh, is essentially unaffected both by time and by IPS treatment, while the Hill coefficient remains close to 1 or slightly lower with minor exceptions. These data suggest a true induction mechanism via the synthesis of new enzyme molecules, together with the possibility of modifications in the mode of aggregation of enzyme protomers.