Menaquinone-4, a potent anti-osteoporosis vitamin : Clarification of its intracellular distribution and new physiological function

Menaquinone-4，一种有效的抗骨质疏松维生素：阐明其细胞内分布和新的生理功能

基本信息

批准号：
09660127
负责人：
KOMAI Michio
金额：
$ 1.54万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

项目摘要

It was confirmed for the first time by the present study that MK-4 is formed from VK_1 in various tissues (testis, lung, brain, submandibullar gland, heart, spleen, liver, pancreas, and kidney) homegenate system as likely in vivo metabolism described previously by us and suggested by other researchers (Suttie J.W.et at. and Thijssen et at.). The present experiment also revealed that the tissue homegenate factor is indispensable for MK-4 formation, and there was a dose-relationship of used tissue-originated protein that may correspond to the converting enzyme. The fractionation of the homogenate was also undertaken, and the highest activity was observed in the microsomal fraction, and followed by mitochondrial fraction, but the other fractions had almost no activity. Combined these results with the data from the experiment using membrane-solubilizing reagent, Triton X-100, it was suggested that the converting enzyme is probably membrane-associated type, though further studies are necessary. As for the substrate-specificity, the higher activities were observed in the case of VK_1 rather than VK_3 as naphthoquinone ring when GGPP was used as isoprenyl side chain, and also higher activity in the case of GGPP than any other isoprenyl side chains when VK_1 was used as naphthoquinone ring substrate.Results from the experiment using [8-ring]-^<14>C-VK_1 substrate indicate that the VK analogues such as reduced-MK-4, VK^3, reduced VK^1, and MK-4 oxide could be candidates for intermediates products for final MK-4 formation. We have got these results for the first time in the world by improving the extraction method and by synthesizing the reduced form of VK that has been thought to be unstable in a routine laboratory circumstance.

本研究首次证实MK-4是由VK_1在多种组织（睾丸、肺、脑、颌下腺、心脏、脾、肝、胰、肾）同源系统中形成的，并可能在体内代谢。我们之前描述过并由其他研究人员建议（Suttie J.W.et at. 和 Thijssen et at.）。本实验还揭示了组织同源因子对于MK-4的形成是不可缺少的，并且所使用的组织源性蛋白存在剂量关系，其可能与转化酶相对应。还对匀浆进行分级分离，在微粒体级分中观察到最高活性，其次是线粒体级分，但其他级分几乎没有活性。将这些结果与使用膜溶解试剂 Triton X-100 的实验数据相结合，表明转化酶可能是膜相关型，但还需要进一步研究。至于底物特异性，当使用 GGPP 作为异戊二烯基侧链时，在 VK_1 而非 VK_3 作为萘醌环的情况下观察到更高的活性，并且当使用 VK_1 时，在 GGPP 的情况下也比任何其他异戊二烯基侧链都具有更高的活性。用作萘醌环底物。使用[8-环]-^ 14 C-VK_1底物的实验结果表明，VK类似物如因为还原型 MK-4、VK^3、还原型 VK^1 和 MK-4 氧化物可能是最终 MK-4 形成的中间产物的候选者。我们通过改进提取方法并合成在常规实验室环境下被认为不稳定的 VK 还原形式，在世界上首次获得了这些结果。