INHIBITION OF RAT-BRAIN PROSTAGLANDIN-D SYNTHASE BY INORGANIC SELENOCOMPOUNDS

被引:65
作者
ISLAM, F [1 ]
WATANABE, Y [1 ]
MORII, H [1 ]
HAYAISHI, O [1 ]
机构
[1] OSAKA BIOSCI INST, DEPT NEUROSCI, 6-2-4 FURUEDAI, SUITA, OSAKA 565, JAPAN
基金
日本科学技术振兴机构;
关键词
D O I
10.1016/0003-9861(91)90456-S
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Various inorganic selenocompounds dose-dependently inhibited the rat brain prostaglandin (PG) D synthase, both in the purified enzyme preparation and in the crude brain supernatant. All of the quadrivalent selenium compounds tested had a very limited range of IC50 values in the purified enzyme (11-12 μm) and in the brain supernatant (9-15 μm). A divalent selenium compound was also inhibitory, but a hexavalent selenium compound was ineffective. In contrast, organic selenocompounds such as selenomethionine and selenourea had no effect on the PGD synthase activity. Furthermore, sodium sulfate and sodium sulfite up to 10 mm did not inhibit the activity. The inhibition by selenium required the preincubation of the metal with sulfhydryl compounds such as dithiothreitol (DTT), indicating that the formation of selenotrisulfide or some other adduct(s) is essential for the inhibition. Furthermore, the inhibition was reversed by an excess amount of dithiothreitol, suggesting that the selenotrisulfide derivative of DTT binds to the SH group of the PGD synthase. The kinetic analysis revealed the inhibition by selenite to be noncompetitive with a Ki value of 10.1 μm. On the other hand, glutathione-dependent PGD synthase from rat spleen was much less inhibited, and PGF synthase and PGD2 11-ketoreductase activities were not inhibited by the selenium compound. © 1991.
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页码:161 / 166
页数:6
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