Developmental kinetics of juvenile hormone inactivation in queen and worker castes of the honey bee, Apis mellifera

Abstract

The kinetics of in vitro juvenile hormone-I inactivation during development, beginning from 2.5 days old larvae to the pupal stage (Pw), was followed in worker and queen castes of the honey bee, Apis mellifera. Juvenile hormone degrading enzymes are present in the larval homogenates of both the castes. The profile of JH-degradation shows high and specific enzyme activity peaks in the initial period of development, i.e. from 2.5 to 3.5 days. Between 4 to 5 days the level of JH-degrading enzymes is very low and reaches thereafter another peak of activity during the stage of pharate pupa. In comparison with worker larvae, queen larvae possess significantly higher specific as well as absolute enzyme activities. Ester hydrolysis mediated by JH-specific esterases is the major pathway of JH-deactivation. Larval homogenate when fortified with NADPH 2 did not show any significant increase in the amount of JH-degradation. In presence of Triton X-100 (0.5%), JH-esterase activity is inhibited to the extent of 85%. JH-esterase activity is principally located in the cytosol while microsomal and mitochondrial fractions were found to be inactive in this respect.