Ecdysone Metabolism in Diapause Eggs and Non-Diapause Eggs of the Silkworm, Bombyx mori

Makka, Toshihiro; Sonobe, Haruyuki

doi:10.2108/zsj.17.89

Cited by 25 publications

(19 citation statements)

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“…9A). This result is consistent with our previous results obtained from tracer experiments using [ 3 H]E22P and [ 3 H]20E22P (18), in which it has been demonstrated that the hydrolysis of ecdysteroid-phosphates is one of the effective causes leading to the increase in the amounts of free ecdysteroids. Furthermore, the pattern of changes in EPPase activity coincided with the changes in the expression pattern of the EPPase transcript (Fig.…”

Section: Discussionsupporting

confidence: 93%

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Purification, Kinetic Characterization, and Molecular Cloning of a Novel Enzyme Ecdysteroid-phosphate Phosphatase

Yamada

Sonobe

2003

Journal of Biological Chemistry

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From eggs of the silkworm Bombyx mori, we isolated a novel enzyme that is involved in the conversion of physiologically inactive conjugated ecdysteroids, such as ecdysone 22-phosphate and 20-hydroxyecdysone 22-phosphate, to active free ecdysteroids. This enzyme, called ecdysteroid-phosphate phosphatase (EPPase), was located in the cytosol fraction and differed from nonspecific lysosomal acid phosphatases in various enzymic properties. EPPase was purified about 3,000-fold to homogeneity by seven steps of column chromatography. The cDNA clone encoding EPPase was isolated by reverse transcription polymerase chain reaction using degenerate primers on the basis of the partial amino acid sequence obtained from purified EPPase and by subsequent 3-and 5-rapid amplification of cDNA ends. The full-length cDNA of EPPase was found to be composed of 1620 bp with an open reading frame encoding a protein of 331 amino acid residues. A data base search showed that there was no functional protein with the amino acid sequence identical to that of EPPase. Northern blot analysis revealed that EPPase mRNA was expressed predominantly during gastrulation and organogenesis in nondiapause eggs but was not detected in diapause eggs whose development was arrested at the late gastrula stage. In nondiapause eggs, the developmental changes in the expression pattern of EPPase mRNA corresponded closely to changes in the enzyme activity and in the amounts of free ecdysteroids in eggs.In insects, ecdysteroids, which regulate development and reproduction, are synthesized in prothoracic glands. However, in many insect species, ecdysteroids have been demonstrated to be synthesized in ovaries as well, to accumulate in mature ovaries, and to be transferred to eggs (1-3). Most of these ecdysteroids are physiologically inactive phosphoric esters and synthesized by the enzyme, ATP:ecdysteroid-phosphotransferase (ecdysteroid kinase), which catalyzes phosphorylation of ecdysteroids ( Fig. 1) (4,5). It has been suggested that free ecdysteroids are liberated from maternal ecdysteroid-phosphates during embryonic development and participate in the secretion of serosal cuticle and/or the induction of embryonic cuticulogenesis (embryonic molt) in various insects, such as Locusta migratoria (6), Schistocerca greagaria (7), Blaberus craniifer (8), and Manduca sexta (9). Furthermore, the involvement of ecdysteroids in embryonic diapause has also been suggested in Lepidosphes ulmi (10), Bombyx mori (11), and L. migratoria (12).In B. mori, recently, it has been demonstrated that the continuous supply of 20-hydroxyecdysone (20E), 1 which has been demonstrated to be an active molecule in B. mori eggs (13), is required for embryonic development and that a deficiency of 20E induces embryonic diapause (13); that is, the cessation of embryonic development at the late gastrula stage (14,15). Furthermore, 20E was demonstrated to be formed by de novo synthesis (16 -18) and dephosphorylation of 20-hydroxyecdysone 22-phosphate (20E22P) and ecdysone 22-phosphate (E22P) (in the c...

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Section: Discussionsupporting

confidence: 93%

“…Furthermore, 20E was demonstrated to be formed by de novo synthesis (16 -18) and dephosphorylation of 20-hydroxyecdysone 22-phosphate (20E22P) and ecdysone 22-phosphate (E22P) (in the case of the latter, dephosphorylation was followed by hydroxylation at C-20 position) (18).…”

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confidence: 99%

Purification, Kinetic Characterization, and Molecular Cloning of a Novel Enzyme Ecdysteroid-phosphate Phosphatase

Yamada

Sonobe

2003

Journal of Biological Chemistry

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“…The activity in the nondiapause eggs gradually increased over the first few days, and then rose rapidly until day 4 (0.8^0.1 pmol´min 21´m g 21 protein). This elevation in the hydroxylation activity coincided with that in the content of 20-hydroxyecdysone [6]. The enzyme activity then gradually decreased, being scarcely detectable on the ninth day (0.025^0.03 pmol´min 21´m g 21 protein).…”

Section: Ecdysone 20-hydroxylation Activity and Level Of Microsomal Pmentioning

confidence: 67%

Molecular cloning of NADPH-cytochrome P450 oxidoreductase from silkworm eggs. Its involvement in 20-hydroxyecdysone biosynthesis during embryonic development

Horike¹,

Takemori²,

Nonaka³

et al. 2000

Eur J Biochem

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Using RT-PCR, a cDNA fragment of NADPH-cytochrome P450 oxidoreductase from silkworm, Bombyx mori, was cloned from three-day-old nondiapause eggs. RACE was used to isolate the ends of the DNA. The fulllength cDNA obtained was composed of 3471 bp with an open reading frame encoding a protein of 687 aminoacid residues with a relative molecular mass of 77 700. The protein, fused with glutathione S-transferase, was expressed in Escherichia coli and purified to homogeneity. The fused protein not only had NADPHdependent cytochrome c-reducing activity, but also acted as an electron carrier from NADPH to bovine adrenal 21-hydroxylase P450 in the steroid hydroxylation reaction, confirming that the protein is the silkworm NADPHcytochrome P450 oxidoreductase. Ecdysone 20-hydroxylase activity in the nondiapause egg microsomes increased until the fourth day after oviposition, and then decreased, little being detected on the ninth day. An antibody raised against the P450 reductase inhibited the ecdysone hydroxylation. Immunoblot analyses of the microsomes indicated that the P450 reductase protein appeared distinctly in the three-day-old nondiapause eggs and, in contrast to the developmental pattern of ecdysone hydroxylase activity, continued to increase as the embryos developed. These results suggest that ecdysone hydroxylation in the early stage of embryogenesis is dependent on the presence of both P450 reductase and ecdysone 20-hydroxylase P450, but its gradual reduction in the later stage may be due to the decrease in the level of ecdysone 20-hydroxylase P450.

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“…In B. mori (21,49), Lepidosaphes ulmi (50), and Locusta migratoria (51), 20-hydroxyecdysone plays an indispensable role in the developmental difference between diapause eggs and nondiapause eggs. In B. mori eggs, 20-hydroxyecdysone has been demonstrated to originate from both de novo biosynthesis (23,38,52,53) and dephosphorylation of ovary-derived ecdysteroid phosphates (27)(28)(29)53). Furthermore, in L. migratoria (54), S. gregaria (55), Blaberus craniifer (56), and Manduca sexta (14,15), free ecdysteroids liberated from ovary-derived ecdysteroid phosphates are suggested to participate in controlling the early events of embryonic development, such as embryonic cuticulogenesis and germ band elongation, which occur before the prothoracic glands differentiate during embryonic development.…”

Section: Discussionmentioning

confidence: 99%

Purification, Kinetic Characterization, and Molecular Cloning of a Novel Enzyme, Ecdysteroid 22-Kinase

Sonobe

Ohira

Ieki

et al. 2006

Journal of Biological Chemistry

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This is the first report succeeding in the isolation and characterization of an enzyme and its gene involved in the phosphorylation of a steroid hormone. It has been demonstrated that ecdysteroid 22-phosphates in insect ovaries, which are physiologically inactive, serve as a "reservoir" that supplies active free ecdysteroids during early embryonic development and that their dephosphorylation is catalyzed by a specific enzyme, ecdysteroid-phosphate phosphatase (Yamada, R., and Sonobe, H. In steroid metabolism, it is generally accepted that cytochrome P450-mediated reaction, referred to as phase I metabolism, converts hydrophobic compounds into more polar metabolites, whereas phase II metabolism involves an adduct formation via a conjugation reaction. Phase II metabolism, such as sulfation, glucuronidation, and fatty acyl esterification, leads to a change of polarity or to a charge modification of the given metabolite, thereby modulating biological activity or facilitating elimination. In mammals, the sulfation pathway can be thought of as a reversible process, comprising two enzyme systems: the sulfotransferases, which catalyze the sulfation reaction, and the sulfatases, which catalyze the hydrolysis of sulfate esters formed by the action of sulfotransferases. Much is now known concerning the function of these enzyme systems as well as the molecular structure of the relevant cDNA and genes comprising these systems (1-4). However, to our knowledge, there exists very little information regarding the phosphorylation of steroid hormones in mammals.Ecdysteroids, which include the arthropod molting hormone, mediate a wide variety of developmental and reproductive events in insects (5). During the larval and pupal stages, ecdysteroids are synthesized in steroidogenic glands, known as the prothoracic glands (6). The detailed ecdysteroid biosynthetic pathway constituted by phase I metabolism is not fully clarified, but cytochrome P450 enzymes catalyzing the last four steps of the biosynthesis of 20-hydroxyecdysone (the principal molting hormone of arthropods) (i.e. CYP306a1 (25-hydroxylase), CYP302a1 (22-hydroxylase), CYP315a1 (2-hydroxylase), and CYP314a1 (20-hydroxylase)), have been identified and characterized in Drosophila melanogaster, Bombyx mori, and Aedes aeypti (7-13).Although glucosides (14), fatty acyl esters (15), and sulfate esters (16) of ecdysteroids are detected as minor products of phase II reaction in several insect species, the major products of the phase II reaction in most insect species are phosphate esters (17-20). The ovaries of most insect species have the capacity to accumulate ecdysteroid phosphates, which are physiologically inactive (21), in addition to the capacity to synthesize free ecdysteroids de novo (22,23). It has been suggested that the ecdystreoid phosphates that are accumulated in the ovaries are transferred to the eggs and function as a source of active free ecdysteroid before the prothoracic glands differentiate during embryonic development (24 -26). Recently, in B. mori eggs, a no...

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Ecdysone Metabolism in Diapause Eggs and Non-Diapause Eggs of the Silkworm, Bombyx mori

Cited by 25 publications

References 9 publications

Purification, Kinetic Characterization, and Molecular Cloning of a Novel Enzyme Ecdysteroid-phosphate Phosphatase

Purification, Kinetic Characterization, and Molecular Cloning of a Novel Enzyme Ecdysteroid-phosphate Phosphatase

Molecular cloning of NADPH-cytochrome P450 oxidoreductase from silkworm eggs. Its involvement in 20-hydroxyecdysone biosynthesis during embryonic development

Purification, Kinetic Characterization, and Molecular Cloning of a Novel Enzyme, Ecdysteroid 22-Kinase

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