CHARACTERIZATION AND TEMPORAL ASPECTS OF HEMOLYMPH JUVENILE-HORMONE ESTERASE IN ADULT COCKROACH, PERIPLANETA-AMERICANA

Daily variations in the in vitro haemolymph juvenile hormone esterase activity (hJHE) of adult male and female Periplaneta americana were mo nitored over a 2 week period from the time of adult emergence, and thr oughout the first reproductive cycle of the adult female, Kinetic anal ysis of hJHE from females indicated an apparent K-m JH III of 5.59 +/- 1.75 mu M (V-max = 140 pmol JH III hydrolysed h(-1) per mu l haemolym ph), In females the mean rate of JH III metabolism in diluted haemolym ph shortly after emergence was 27.5 +/- 1.5 pmol h(-1) mu l(-1) (n = 1 6) and remained relatively low (16-32 pmol h(-1) mu l(-1)) over much o f early adult development. Activity remained at this level during the first two days of the 4 day reproductive cycle, but showed a much incr eased broad peak of activity (74-93 pmol h(-1) mu l(-1)) at 60-72 h po st-extrusion. This peak lags behind the whole body JH titre peak, whic h could suggest that elevated levels of JH III may bring about the ind uction of JH esterase(s). A different pattern of JHE activity was obse rved in adult males, hJHE rates in males at emergence were almost twic e as high (81.5 +/- 15.8 pmol h(-1) mu l(-1), n = 16) as those found i n females at this time, but thereafter showed a downturn to moderate l evels (44-68 pmol h(-1) mu l(-1)) that were maintained for the remaind er of the study, Rapid (FPLC) DEAE-sepharose ion exchange chromatograp hy, ultrafiltration and fast-pow superose gel filtration chromatograph y were employed to achieve an efficient partial purification (166-fold ) of the hJHE from cell-free plasma of reproductively active female P. americana 48-72 h post-ootheca extrusion, Gel filtration and SDS-poly acrylamide gel electrophoresis (PAGE) revealed an enzyme having appare nt molecular mass of between 60 and 70 MDa, whilst non-denaturing PAGE and iso-electrofocusing resolved a single acidic enzyme peak with a p I of 4.9. (C) 1997 Elsevier Science Ltd.