1998 Fiscal Year Final Research Report Summary
A new reaction scheme of steroidogenic membrane enzymes and its physiological meanings.
| Project/Area Number |
09680623
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Functional biochemistry
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| Research Institution | HIROSHIMA UNIVERSITY |
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Principal Investigator |
KOMINAMI Shiro Hiroshima Univ.Fac.Integrated Arts and Sciences, Professor, 総合科学部, 教授 (10106776)
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| Co-Investigator(Kenkyū-buntansha) |
YMAZAKI Takeshi Hiroshima Univ.Fac.Integrated Arts and Sciences, Associate Professor, 総合科学部, 助教授 (30192397)
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| Project Period (FY) |
1997 – 1998
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| Keywords | P4517alpha / P45011beta / Successive Reactions / Steroidogenesis / Aldosterone / ACTH / Neurosteroid / Nitri oxide synthase |
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| Research Abstract |
Bovine adrenal cytochrome P45017alpha can catalyze 17alpha-hydroxylation for progesterone and pregnenol one but can produce androgen only from pregnenolone. In this study, it is demonstrated that the rate of release of the 17alpha-hydroxyprogesterone from the enzyme is much faster than the subsequent oxygenation reaction, which is the main reason for the 17alpha-hydroxyprogesterone could not be further metabolized to androstenedione.
Bovine adrenal P450llbeta converts deoxycorticosterone to corticosterone and further to aldosterone but in the presence of P45Oscc P450llbeta only catalyzes the conversion to corticosterone. The interaction of P450llbeta with P450scc accelerates the release of cortico- sterone from P450llbeta, which prevents the further metabolism to aldosterone.
o-Nitrophenylsufenyl adrenocorticotropin (NPS- ACTH) and ACTH can stimulate adrenal steroidogenesis. In this study, the second messengers for the acute stimulation (-15 min) are investigated. By using various specific inhibitors, 15-HPETE and cAMP were found to be the second messengers for the acute stimulation. Furthermore, the stimulation correlates very well to the increase in the Ca ion concentration in the cells, which was measured by the video-enhanced Ca-fluorescence technique. The Ca channel blocker inhibits completely the stimulation, which confirms for Ca to be the second messenger for the stimulation.
The localization of the steroidogenic sites in brain was investigated using anti-P45Oscc- IgG.It is clearly sown that Purkinje cells have P45Oscc which produces pregnenolone from cholesterol. The reaction of nitric oxide synthase was investigated using purified recombinant enzyme, where the reaction scheme of NOS was the same as that of P450 successive reactions.
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