Johan L, van Haarlem M, Soute B A, Vermeer C
Department of Biochemistry, University of Limburg, Maastricht, The Netherlands.
FEBS Lett. 1987 Oct 5;222(2):353-7. doi: 10.1016/0014-5793(87)80401-5.
In the liver vitamin K epoxide, which is produced during the posttranslational carboxylation of protein-bound glutamic acid residues, is recycled by the action of one or more dithiol-dependent reductases. In vitro synthetic dithiols may serve as a cofactor for these enzymes, but the physiological reductant has not yet been found. In this paper we report that in vitro the commercially available thioredoxin/thioredoxin reductase from E. coli can replace the synthetic dithiols during the various reactions of the vitamin K cycle. Based on the assumption that in vivo thioredoxin also plays a role in the regeneration of vitamin K hydroquinone from the epoxide, an extension of the generally accepted vitamin K cycle is proposed.
在肝脏中，蛋白质结合的谷氨酸残基进行翻译后羧化过程中产生的维生素K环氧化物，通过一种或多种二硫醇依赖性还原酶的作用进行循环利用。体外合成的二硫醇可作为这些酶的辅因子，但尚未发现生理性还原剂。在本文中，我们报告了在体外，市售的来自大肠杆菌的硫氧还蛋白/硫氧还蛋白还原酶在维生素K循环的各种反应中可以替代合成二硫醇。基于硫氧还蛋白在体内也参与从环氧化物再生维生素K氢醌的假设，提出了对普遍接受的维生素K循环的扩展。
