Lethal metabolism of precocene-I to a reactive epoxide by locust corpora allata

Pratt, G. E.; Jennings, Richard C.; Hamnett, Anthony F.; Brooks, G. T.

doi:10.1038/284320a0

Cited by 153 publications

(51 citation statements)

References 21 publications

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“…The present studies are important in connection with the recently discovered oxidative bioactivation of the anti-allatal agents (precocenes) in this species [10,33]. It has been suggested [lo] that the selective cytocidal action of precocenes in sensitive species may result from the high levels of epoxidase in the cells of their corpora allata.…”

Section: Discussionmentioning

confidence: 99%

Enzymic Synthesis of Juvenile Hormone in Locust Corpora Allata: Evidence for a Microsomal Cytochrome P‐450 Linked Methyl Farnesoate Epoxidase

Feyereisen

Pratt

Hamnett

1981

European Journal of Biochemistry

103

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Homogenates of corpora allata from adult Locusta migratoria in phosphate‐buffered EDTA have been analysed by sucrose‐density‐gradient centrifugation. Succinate‐cytochrome c reductase activity (mitochondrial) bands between d204 1.13–1.15, whereas NADPH‐cytochrome c reductase and NADPH–dependent methyl farnesoate 10, 11‐epoxidase activities band identically between d204 1.06–1.12. We conclude that the methyl farnesoate epoxidase is exclusively microsomal. Farnesoic acid O‐methyltransferase is an exclusively soluble enzyme which stoichiometrically transfers the S‐methyl group from S‐adenosylmethionine to farnesoic acid. No carboxyl esterase activity was found. Isolated microsomes were used to obtain an apparent Km= 7.7 × 10−6 M for the epoxidase, although substrate solubility limits the rate to 0.5 V As expected, the product (juvenile hormone III) is chiral (10 R). The epoxidase is inhibited by excess NADP+ and oxidised cytochrome c, but neither inhibited nor synergised by NADH. NADH supports less than 10% of the NADPH rate of epoxidation. The epoxidase is inhibited by a carbon monoxide/oxygen atmosphere, half‐maximal inhibition occurring at a CO/O2 ratio of 4.0. This inhibition is reversed by white‐light irradiation.

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Section: Discussionmentioning

confidence: 99%

Enzymic Synthesis of Juvenile Hormone in Locust Corpora Allata: Evidence for a Microsomal Cytochrome P‐450 Linked Methyl Farnesoate Epoxidase

Feyereisen

Pratt

Hamnett

1981

European Journal of Biochemistry

103

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“…The inhibition of oviposition by a chemical may be caused by blocking the necessary endocrine secretion (Pratt et al, 1980), inhibition of ovarian development or malformation of ovipositing organs (Asai et al, 1985). A significant reduction (pϽ0.05) in fecundity on the treated diet after both male and female treatment may be due to the exposure of parents for a longer duration including egg laying period also.…”

Section: Discussionmentioning

confidence: 99%

Effects of sublethal doses of beta-cyfluthrin on mutant Drosophila melanogaster (Diptera: Drosophilidae)

Nadda

Saxena

Srivastava

2005

Appl. Entomol. Zool.

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Laboratory experiment was conducted to examine sublethal effects of beta-cyfluthrin (Bulldock ® 025 SC) on the sepia mutant of Drosophila melanogaster at a temperature of 25Ϯ0.5°C, 50Ϯ5% relative humidity and a photoperiod of 16 : 8 (light : dark) hours. Males and females were exposed separately to beta-cyfluthrin (one tenth of the calculated LC 50 value) mixed in the diet for 24, 48 and 72 h. Fecundity, hatchability, pupation, adult emergence, larval, pupal and total developmental periods were evaluated in the F 1 generation after various cross combinations. A reduction in fecundity, egg hatching, number of larvae, pupae, adults and prolongation of larval, pupal and total developmental periods was observed. A significant reduction (pϽ0.05) in fecundity was observed only on the treated diet after treatment of both the sexes. Maximum effects were observed after 72 h treatment followed by 48 and 24 h. Males were found to be more susceptible to beta-cyfluthrin as compared to the females.

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“…One potential candidate was methyl farnesoate epoxidase, but our study surprisingly does not support this hypothesis. It seemed logical 20 years ago to assume that the enzyme responsible for the bioactivation of precocenes was methyl farnesoate epoxidase because inhibition and destruction of the CA could be observed in vitro, the effects of precocenes were sensitive to P450 inhibitors, and the allatal epoxidation of precocene I was shown to be stereospecific (32)(33)(34)(35). However, inhibition of JH production by isolated glands occurs only at very high precocene concentrations (33,35), and precocene sensitivity is independent of the intrinsic activity of the glands (33,36).…”

Section: Expression Of Cyp15a1 In the Cockroach: Tissue And Developmementioning

confidence: 99%

“…Precocenes are anti-juvenile hormones (30) described as a pro-allatocidins (31,32) acting directly on the CA of sensitive insects to cause anti-JH effects by causing necrosis of the glands. Their mode of action involves metabolic activation within the glands by a cytochrome P450.…”

Section: Expression Of Cyp15a1 In the Cockroach: Tissue And Developmementioning

confidence: 99%

CYP15A1, the cytochrome P450 that catalyzes epoxidation of methyl farnesoate to juvenile hormone III in cockroach corpora allata

Helvig

Koener

Unnithan

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

224

237

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The molecular analysis of insect hormone biosynthesis has long been hampered by the minute size of the endocrine glands producing them. Expressed sequence tags from the corpora allata of the cockroach Diploptera punctata yielded a new cytochrome P450, CYP15A1. Its full-length cDNA encoded a 493-aa protein that has only 34% amino acid identity with CYP4C7, a terpenoid -hydroxylase previously cloned from this tissue. Heterologous expression of the cDNA in Escherichia coli produced >300 nmol of CYP15A1 per liter of culture. After purification, its catalytic activity was reconstituted by using phospholipids and house fly P450 reductase. CYP15A1 metabolizes methyl (2E,6E)-3,7,11-trimethyl-2,6-dodecatrienoate (methyl farnesoate) to methyl (2E,6E)-(10R)-10,11-epoxy-3,7,11-trimethyl-2,6-dodecadienoate [juvenile hormone III, JH III] with a turnover of 3-5 nmol͞min͞nmol P450. The enzyme produces JH III with a ratio of Ϸ98:2 in favor of the natural (10R)-epoxide enantiomer. This result is in contrast to other insect P450s, such as CYP6A1, that epoxidize methyl farnesoate with lower regio-and stereoselectivity. RT-PCR experiments show that the CYP15A1 gene is expressed selectively in the corpora allata of D. punctata, at the time of maximal JH production by the glands. We thus report the cloning and functional expression of a gene involved in an insectspecific step of juvenile hormone biosynthesis. Heterologously expressed CYP15A1 from D. punctata or its ortholog from economically important species may be useful in the design and screening of selective insect control agents.

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Lethal metabolism of precocene-I to a reactive epoxide by locust corpora allata

Cited by 153 publications

References 21 publications

Enzymic Synthesis of Juvenile Hormone in Locust Corpora Allata: Evidence for a Microsomal Cytochrome P‐450 Linked Methyl Farnesoate Epoxidase

Enzymic Synthesis of Juvenile Hormone in Locust Corpora Allata: Evidence for a Microsomal Cytochrome P‐450 Linked Methyl Farnesoate Epoxidase

Effects of sublethal doses of beta-cyfluthrin on mutant Drosophila melanogaster (Diptera: Drosophilidae)

CYP15A1, the cytochrome P450 that catalyzes epoxidation of methyl farnesoate to juvenile hormone III in cockroach corpora allata

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