Characterization of the Juvenile Hormone Esterases During Embryogenesis of the House Cricket,Acheta domesticus

Esterase and lipase in camel tick Hyalomma dromedarii (Acari: Ixodidae) during embryogenesis

Esterase and lipase activity showed significant changes during embryogenesis of camel tick Hyalomma dromedarii. From the elution profile of chromatography on DEAE-cellulose, six forms of H. dromedarii esterase (El to EVI) can be distinguished. Esterase EIII was purified to homogeneity after chromatography on Sepharose 6B. The molecular mass of esterase EIII was 45 kDa for the native enzyme and represented a monomer of 45 kDa by SDS-PAGE. Esterase EIII had an acidic pI at 5.3. Lipase activity was detected in the same DEAE-cellulose peaks (LI to LVI) of H. dromedarii esterases. The highest lipase activity was exhibited by lipase LIII. Esterase EIII and lipase LIII were compared with respect to Michaelis constant, substrate specificity, temperature optimum, heat stability, pH optimum, effect of metal ions and inhibitors. This study suggests that H. dromedarii lipolytic enzymes may play a central role in the interconversion of lipovitellins during embryogenesis.

Stage-specific production and release of juvenile hormone esterase from the ovary of Diploptera punctata

Juvenile hormone esterase (JHE) is a catabolic enzyme that specifically degrades juvenile hormone (JH) and has been identified in hemolymph and tissues in both larvae and adults of numerous insect species. This study investigates the presence of JHE in ovaries of the viviparous cockroach, Diploptera punctata, and the in vitro release of JHE from these ovaries during the first gonadotrophic cycle. JHE is released in vitro from maturing basal (most posterior) follicles and from follicle cells isolated from oocytes during the short period of time between spermatophore release and chorion formation. Enzyme release is dependent upon the presence of calcium in the medium. This released ovarian JHE appears to be larger than and to display ionic characteristics that are different from the isolated hemolymph and fat body JHEs. In addition, JHE activity measured in homogenates of whole ovaries and subsequently oviposited basal oocytes increases dramatically following spermatophore release, coincident with a previously described decline in JH titer in the ovary. A likely role for ovarian JHE is the site-specific degradation of JH in and around the oocyte prior to fertilization and embryonic development.

A partition assay for the simultaneous determination of insect juvenile hormone esterase and epoxide hydrolase activity

A partition assay was developed to measure insect juvenile hormone (JH) I and III metabolism in biological samples containing both JH esterase and JH epoxide hydrolase activity. The assay utilizes commercially available radiochain 3H-labeled JH as substrate and the selective JH esterase inhibitor 3-octylthio-1,1,1-trifluoro-2-propanone. JH partitions into an isooctane phase and the metabolites JH acid, JH diol, and JH diol-acid into aqueous methanol after incubation of JH substrate with inhibited and uninhibited sample. The assay provides a time- and cost-efficient alternative to the currently available thin-layer chromatography method for the measurement of JH esterase and epoxide hydrolase activity.