VITAMIN-K EPOXIDE AND QUINONE REDUCTASE ACTIVITIES - EVIDENCE FOR REDUCTION BY A COMMON ENZYME

被引:21
作者
GARDILL, SL [1 ]
SUTTIE, JW [1 ]
机构
[1] UNIV WISCONSIN,COLL AGR & LIFE SCI,DEPT BIOCHEM,MADISON,WI 53706
关键词
D O I
10.1016/0006-2952(90)90493-5
中图分类号
R9 [药学];
学科分类号
1007 ;
摘要
Vitamin K hydroquinone formation in rat liver can be catalyzed by a thiol-dependent quinone reductase activity which shares several characteristics with the vitamin K 2,3-epoxide reductase activity. The possibility that a single enzyme catalyzes both reductions was investigated. Values of Vmax/Km for several different vitamin K analogs were determined and found to be similar for both reductase activities. Several different coumarins were also shown to achieve 50% inhibition at similar concentrations for both enzyme activities. The chloro analog of menaquinone-2 was shown to inhibit both reductases, and the presence of either the quinone or epoxide form of the vitamin protected both activities from inactivation. Thioredoxin was shown to function as a reductant for both reductase activities, although the maximum enzyme activity achieved by this reductant was only half that achieved with dithiothreitol as a reductant. Cofractionation of the two reductase activities on a variety of column matrices was also observed. These data strongly support the hypothesis that one microsomal enzyme is capable of catalyzing both reduction of vitamin K 2,3-epoxide to the quinone, and the quinone to vitamin K hydroquinone. © 1990.
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页码:1055 / 1061
页数:7
相关论文
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