de Metz M, Soute B A, Hemker H C, Fokkens R, Lugtenburg J, Vermeer C
J Biol Chem. 1982 May 25;257(10):5326-9.
In addition to the three known forms of vitamin K (vitamin K quinone, vitamin K hydroquinone, and vitamin K epoxide), a fourth metabolite, hydroxyvitamin K, was found in reaction mixtures containing a vitamin K-dependent carboxylating enzyme system. When sulfite was added to such reaction mixtures, the formation of hydroxyvitamin K was substantially enhanced, whereas no epoxide was formed anymore. The vitamin K-dependent carboxylation was stimulated at these sulfite concentrations. Vitamin K hydroquinone could be replaced by t-butylhydroperoxide and also under these conditions the carboxylation was enhanced by sulfite. In the presence of peroxidase, the carboxylation reaction was blocked, whereas hydroxyvitamin K could still be detected in the reaction mixtures, even in the absence of sulfite. These observations lead us to the hypothesis that the carboxylation of glutamic acid residues is coupled to the heterolytic cleavage of a peroxide bond with the concurrent formation of vitamin epoxide.
除了维生素K的三种已知形式（维生素K醌、维生素K氢醌和维生素K环氧化物）外，在含有维生素K依赖性羧化酶系统的反应混合物中发现了第四种代谢物——羟基维生素K。当向此类反应混合物中添加亚硫酸盐时，羟基维生素K的形成显著增强，而不再形成环氧化物。在这些亚硫酸盐浓度下，维生素K依赖性羧化反应受到刺激。维生素K氢醌可以被叔丁基过氧化氢替代，并且在这些条件下，羧化反应也会被亚硫酸盐增强。在过氧化物酶存在的情况下，羧化反应被阻断，而即使在没有亚硫酸盐的情况下，反应混合物中仍可检测到羟基维生素K。这些观察结果使我们提出一个假设，即谷氨酸残基的羧化与过氧化物键的异裂以及同时形成维生素环氧化物有关。
