Juvenile Hormone Esterase Activity Research Articles

Control of juvenile hormone esterase activity in Galleria mellonella larvae

The juvenile hormone esterase (JHE) activity in Galleria mellonella larvae was measured after exposure to different experimental conditions that affect larval-pupal transformation. The data show that stimulation of production of JHE is closely coupled with the developmental signals that intiate larval-pupal metamorphosis. Injury, which delays pupation, delays the appearance of JHE activity if the larvae are injured within 48 hr after the last larval moult. Chilling of day-0 larvae induces a supernumerary larval moult and inhibits the appearance of JHE. However, JHE activity increases in chilled larvae when their commitment for an extra larval moult is reversed by starvation. Starvation is effective in reversing the commitment for an extra larval moult if commenced within 48 hr after chilling, thereby suggesting a critical period for that commitment. These data suggest that the stimulus for JHE synthesis and/or release occurs approximately within 48 hr after the last larval ecdysis. A series of studies involving implantation of brain, suboesophageal ganglion and fat body into chilled, as well as chilled and ligated larvae suggest that a factor from the brain is involved in stimulation or production of JHE in Galleria larvae. JH, which suppresses JHE activity in day-3, -5 and early day-6 Galleria larvae, stimulates the production of JHE in late day-6 larvae, suggesting that reprogramming in larval fat body may occur on day 6 of the last larval stadium.

Juvenile hormone metabolism and juvenile hormone esterase titer in hemolymph and peripheral tissues ofDrosophila hydei

Third larval instar hemolymph of the fruitflyDrosophila hydei did not metabolize juvenile hormone (JH) at all developmental stages. In contrast, prepupal and pupal body fluid showed JH-esterase activity with a maximum at 4 h after puparium formation. In body wall and fat body of all developmental stages investigated, JH-metabolic activity was found. In both tissues JH catabolism was most active in the 120,000g supernatant and pellet. The 800g and 15,000g pellet showed a lower activity. In all subcellular fractions the JH-acid was identified as the predominant metabolite. There is evidence that JH-specific esterases are responsible for ester cleavage in the 120,000g supernatant. During mid and late third larval instar development in both body wall and fat body JH-esterase activity remains relatively constant.

Effects of the anti hormone-hormone mimic ETB on the induction of insect juvenile hormone esterase in [formula omitted][formula omitted

Juvenile hormone (JH) esterases can be artificially induced to appear in the hemolymph of last instar larvae of the lepidopterous insect Trichoplusia ni (Noctuidae) by topical treatment with JH I, JH II, or dihomo branched juvenoids. ETB (ethyl-4-[2-(t-butylcarbonyloxy) butoxy] benzoate; ZR-2646) at high doses is a weak inducer of JH esterase (JHE). However, at doses of ETB that induce only low levels of JHE activity, ETB will block the JHE induction caused by the dihomo juvenoid epofenonane and at higher doses will reduce the induction caused by JH I or JH II. ETB is not a JHE inhibitor; rather, it appears to be acting as a JH agonist/antagonist in normal larvae and in isolated abdomens. These effects of ETB on JHE induction may illustrate a new mode of action of anti-JH's.

Correlations between juvenile hormone esterase activity, ecdysone titre and cellular reprogramming in Galleria mellonella

Juvenile hormone esterase (JHE) activity, ecdysone titre, and developmental competence of the epidermis were determined in last instar larvae and pupae of Galleria mellonella. Haemolymph JHE activity reaches a peak before increases are observed in ecdysone titre both during larval-pupal and pupal-adult metamorphosis. JHE activity is low during the penultimate larval instar although general esterase activity is relatively high. In last instar larvae two ecdysone peaks are noted after the increase in JHE activity. Furthermore, epidermal cell reprogramming occurs just after the increase in haemolymph JHE activity and possibly before the first increase in ecdysone titre. This was tested by injection of high doses of β-ecdysone into last instar larvae of different ages resulting in rapid cuticle deposition. Reprogramming occurred if the resulting cuticle was of the pupal type. These correlative observations may increase our understanding of the relative importance of an ecdysone surge in the absence of JH in reprogramming of the insect epidermis.

A comparison of the induced and naturally occurring juvenile hormone esterases from last instar larvae of Trichoplusia ni

During the last larval instar of Trichoplusia ni two naturally occurring peaks of juvenile hormone esterase activity are present. After a critical period, juvenile hormone esterase activity can be induced in normal and ligated larvae by the topical application of juvenile hormone or juvenoids. The natural and artificially induced juvenile hormone esterases are similarly inhibited by a selected group of organophosphate and carbamate inhibitors. Paraoxon and O- ethyl-S- phenyl phosphoramidothiolate displayed the best inhibition, both with an I 50 of 1 × 10 −6M, while several general esterase inhibitors, including diisopropyl phosphorofluoridate, had very little effect. The three groups of juvenile hormone esterases have similiar gel filtration patterns which are distinct from most of the α-naphthyl acetate esterase activity. The natural and artificially induced juvenile hormone esterases demonstrated identical migration patterns when analyzed by gel electrophoresis. Isoelectric focusing also resulted in essentially identical activity patterns and pI values for each of the three groups of juvenile hormone esterases. Both naturally occurring peaks of juvenile hormone esterase activity as well as an artificially induced peak of juvenile hormone esterase activity appear to be largely due to one enzyme, and within the limits of the techniques used, these esterases are identical. The juvenile hormone esterase activity is distinct from and more stable than the majority of the α-naphthyl acetate esterase activity in the haemolymph.

Haemolymph juvenile hormone esterase activity in synchronous last instar larvae of the cabbage looper, Trichoplusia ni

Weight and time of moult during the last instar of the cabbage looper ( Trichoplusia ni) were examined and used to select last instar larvae that had similar rates of development. Haemolymph protein content and titres of haemolymph esterases hydrolyzing juvenile hormone I, juvenile hormone III, and α-naphthyl acetate were monitored during the last instar using these closely timed larvae. Juvenile hormone I and juvenile hormone III esterase profiles were very similar and differed markedly from the α-naphthyl acetate esterase and protein content profiles. Two major peaks of juvenile hormone esterase activity were observed, one before ecdysone release and the other just prior to pupal ecdysis. Juvenile hormone I was hydrolyzed 15 times faster than juvenile hormone III when assayed at 5 × 10 −6 M.

Induction and regulation of juvenile hormone esterases during the last larval instar of the cabbage looper, Trichoplusia ni

Juvenile hormone esterase titres were monitored in gate I and gate II last instar larvae of Trichoplusia ni using JH III as substrate. Two peaks of activity were observed for both gate I and gate II larvae, although the first and second juvenile hormone esterase peaks for the gate II larvae are extended and delayed one day, respectively. Head or thoracic ligations before the prepupal stage lower or block the appearance of both esterase peaks. Juvenile hormone I and II, as well as homo and dihomo juvenoids can induce the second juvenile hormone esterase peak in both normal and ligated larvae, and increase the esterase titre during the first peak in nonligated larvae. Induction of the juvenile hormone esterases is possible in non-ligated larvae as soon as the moult to the last instar has occurred and in ligated larvae as soon as the first esterase peak has started to decline. Distinct mechanisms of regulation are present for the first and second juvenile hormone esterase peaks. Juvenile hormone does not appear to be involved in regulating its own metabolism by directly inducing the first esterase peak; however, evidence is consistent with a brief burst of juvenile hormone which occurs prior to pupation inducing the production of the second peak of juvenile hormone esterase activity.

Factors influencing juvenile hormone esterase activity in the wax moth, Galleria mellonella

The effects of juvenile hormone, antiallatotropins, selected surgical procedures and starvation on the juvenile hormone esterase levels in Galleria larvae and pupae were investigated. JH reduced JH esterase activity in larvae but induced the enzyme in 1-day-old pupae. In vitro studies confirmed that the peak of synthesis and/or release of JH esterase from the fat body of last instar larvae occurred 4 days after ecdysis. These studies also showed that fat body from JH-treated larvae released much less enzyme than controls. Antiallatotropins, precocene 2 and ZR 2646 also reduced JH esterase levels in larvae, but ZR 2646 induced JH esterase in pupae. In starved larvae, JH esterase did not increase during the first five days. A minimum of 36 hr of feeding was necessary for the larval esterase activity to increase on schedule on day 4 of the last larval stadium. When day-l larvae were ligated behind the head or the prothorax, they had lower JH esterase levels and yet showed a slight increase in the enzyme when the larvae reached the age of 4 days. The significance of these results is discussed in relation to the possible control of esterase activity during metamorphosis.

Regulation of the activity of JH-specific esterases in the Colorado potato beetle, Leptinotarsa decemlineata

The regulation of haemolymph JH-esterase activity, the main degradation pathway of JH in the Colorado potato beetle, Leptinotarsa decemlineata Say, has been studied by means of JH application and microsurgical techniques. Treatment of diapause beetles with JH 1 and different JH analogues resulted in an increase in JH-esterase activity within 24 hr. Puromycin or actinomycin D treatment prevented the appearance of these enzymes. Ligation and allatectomy experiments performed on diapause beetles suggest, but do not prove conclusively, that this induction phenomenon is an indirect effect of JH. Transfer of short-day beetles to a long-day photoregime and treatment of short-day beetles with JH prevented the occurrence of high levels of JH-esterase activity. On the other hand, allatectomy of short-day beetles resulted in an identical effect. It is very likely that in short-day beetles the occurrence of a low JH titre during the first days after adult emergence is necessary for the induction of the high JH-esterase peak, prior to entering diapause. Whether the effect of JH is direct or indirect still remains unknown. The results suggest that the regulation of haemolymph JH-esterase activity is controlled by a complex of neuro-endocrine factors.

Juvenile hormone epoxide hydrase in house flies, flesh flies and blow flies

Juvenile hormone (JH) epoxide hydrase activity of the house fly ( Musca domestica L.), flesh fly ( Sarcophage bullata Parker), and black blow fly ( Phormia regina (Meigen)) was measured in vitro. Juvenile hormone esterase activity, present in the same in vitro system, was eliminated by the addition of paraoxon. Most of the enzyme is located in the microsomal fractions of insect tissue homogenates. The hydrase is NADPH-independent and is not affected by carbon monoxide or other inhibitors of microsomal oxidases. It is inhibited by certain JH analogs containing an epoxy group. No marked difference in hydrase activity was observed between strains of insecticide-susceptible and resistant house flies. The enzyme is induced in the house fly by feeding phenobarbital for three days.

Selective inhibition of JH esterases from cockroach hemolymph

Juvenile hormone III was tritium labeled on the methyl ester and utilized with other substrates in an investigation of inhibition and substrate specificity of hemolymph esterases from the cockroach, Blaberus giganteus. The structure of labeled juvenile hormone III was supported both chemically and biochemically. Forty-two potential inhibitors were examined, and the best inhibitors included phosphoramidothiolates and S-phenylphosphates. One of these inhibitors was found useful in hormone biosynthesis studies dealing with the enzymatic conversion of methyl farnesoate to juvenile hormone in corpora allata homogenates. Several commonly used inhibitors of carboxyesterases caused only weak inhibition of JH esterases. Gel filtration elution patterns, inhibitor relationships, and specific activities of the hemolymph esterases indicate that juvenile hormones I and III are degraded by similar if not identical enzymes. In some cases, α-naphthyl acetate and juvenile hormone esterase activity could be differentially inhibited. Hemolymph esterases were not capable of degrading ethyl or isopropyl conjugated esters of two juvenoids or three model substrates.

A rapid assay for insect juvenile hormone esterase activity

A rapid new assay is proposed for analyzing insect juvenile hormone esterase activity. The assay is based on . 99% of radiolabeled juvenile hormone being extracted into an isooctane phase while > 99% of the juvenile hormone acid remains in the basic aqueous-methanol phase. The assay is more rapid and less expensive than conventional chromatographic assays while yielding almost identical values of similar precision. This is the first rapid assay proposed for isomerically pure, commercially available juvenile hormone I.

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

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.

Juvenile hormone esterase activity in precisely timed last instar larvae and pharate pupae of Manduca sexta

Juvenile hormone esterase (JHE) from fifth instar Manduca sexta haemolymph was purified 38 fold, treated with DFP and used to determine a K m . Assay parameters for JHE such as partitioning of substrate and product, effect of protein, and time course were determined. Animals staged to within 1.5 hr of ecdysis to the fifth instar were used to determine JHE activity during the instar and pharate pupal life. Two peaks of activity were observed, one just before wandering and the other just before larval-pupal ecdysis.

Age-dependent changes in juvenile hormone esterase and general carboxyesterase activity in the hemolymph of the colorado potato beetle, Leptinotarsa decemlineata

An in vitro method has been developed for the quantitative estimation of juvenile hormone (JH) esterase activity in the hemolymph of the Colorado beetle Leptinotarsa decemlineata Say. The apparent K m value for JH-esterase was determined. JH-esterase and general carboxyesterase activities were estimated throughout the life cycle and under different photoperiodic conditions. High activities were observed in fourth instar larvae and in beetles just before diapause. Lower activities were found in third instar larvae, long-day, diapause and post-diapause beetles. Similar variations were found in general carboxyesterase activity but not in protein concentration. A possible role for the esterase in the regulation of the JH titer is discussed.

Developmental changes of the juvenile hormone esterase activity in haemolymph of the tobacco hornworm, Manduca sexta

The activity of juvenile hormone esterase in Manduca was determined quantitatively by incubating 14C-labelled H. cecropia C 18-juvenile hormone (C 18-JH) with haemolymph drawn from various developmental stages. Activity reaches a major peak on day 3 of the last (fifth) instar; smaller peaks were found'at the time of pupal ecdysis and in young adults of both sexes. Haemolymph of fourth instar larvae and pupae is inactive. These changes are independent of fluctuations in the ‘general esterase’ activity and haemolymph dry weight. A possible role for the esterase in regulation of the JH titre is discussed.