|
In enzymology, juvenile hormone esterase (JH esterase) is an enzyme that catalyzes the hydrolysis of juvenile hormone. For example, the juvenile hormone II (found in ''Lepidoptera''): :methyl (2E,6E)-(10R,11S)-10,11-epoxy-3,7,11-trimethyltrideca-2,6-dienoate + H2O (2E,6E)-(10R,11S)-10,11-epoxy-3,7,11-trimethyltrideca-2,6-dienoic acid + methanol. == Nomenclature and Function == This enzyme belongs to the family of hydrolases, specifically those acting on carboxylic ester bonds. The systematic name of this enzyme class is methyl-(2E,6E)-(10R,11S)-10,11-epoxy-3,7,11-trimethyltrideca-2,6-dienoate acylhydrolase. Other names in common use include: * JH esterase, * juvenile hormone esterase, and * juvenile hormone carboxyesterase. Juvenile hormone (JH) controls insect metamorphosis 〔Gilbert et al., 1977〕). High JH titers maintain the larval state while a decrease in the JH titer initiates the pupation sequence 〔Nijhout and Williams, 1974〕) as well as a change in tissue commitment away from synthesis of larval tissues to pupal tissues at the pupal stage 〔Riddiford, 1976〕). The drop in JH titer at the beginning of the last larval instar in the Lepidoptera appears to be due to a combination of increased metabolism 〔Nowock and GILBERT, 1976a; Sanburg et al., 1975a; Sanburg et al., 1975b〕) and decreased synthesis.〔Nijhout, 1975〕 In the Lepidoptera, JH is initially metabolized by ester hydrolysis;〔Hammock and Quistad, 1976; Slade and Zibitt, 1972〕 esterases capable of hydrolyzing JH are detectable in the hemolymph at times during the last larval instar that appear to coincide with reported drops in the JH titre.〔Vince and Gilbert, 1977:Sparks, 1979 #1170; Weirich and Wren, 1973〕 The JHE's are also selective for the 2E methyl ester of the naturally occurring JH's.〔Hammock et al., 1977; Weirich and Wren, 1973; Weirich and Wren, 1976〕 These studies suggest that the JHE's may be important in the regulation of the JH titre and therefore involved in the initiation of and the commitment to the pupal stage. JHE's appear to be produced by the fat body 〔Hammock et al., 1975; Nowock and Gilbert, 1976b; Whitmore et al., 1974〕 and this production can be stimulated by exogenous JH in Hyalophora pupae, a stage devoid of JHE activity.〔Whitmore, 1972 #1160;Whitmore et al., 1974〕 Stimulation of JHE activity by JH has also been noted recently in adults of Leptinotarsa decemlineata 〔Kramer, 1978〕 and pupae of Galleria mellonella.〔Reddy et al., 1979〕 However, to date, no reported studies have examined this phenomenon during the last larval instar when these enzymes are thought to be of primary importance. Thus this laboratory undertook an investigation of the hemolymph JHE regulation during the last larval instar of the cabbage looper, Trichoplusia ni. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Juvenile-hormone esterase」の詳細全文を読む スポンサード リンク
|