Shineberg B, Young I G
Biochemistry. 1976 Jun 29;15(13):2754-8. doi: 10.1021/bi00658a007.
It has been postulated that 1,4-dihydroxy-2-naphthoic acid is the naphthalenic intermediate in the biosynthesis of menaquinone (vitamin K2) in Escherichia coli to which the octaprenyl side chain is attached to from demethylmenaquinone. In the present work the presence of enzyme, 1,4-dihydroxy-2-naphthoate octaprenyltransferase, which catalyzes the conversion of 1,4-dihydroxy-2-naphthoate to demethylmenaquinone was demonstrated in cell extracts of E. coli. Demethylmenaquinone-9 was formed when the naphthoate was incubated with cell extracts and the synthetic substrate, solanesyl pyrophosphate, in the presence of Triton X-100. Solanesyl monophosphate could not substitute for the pyrophosphate in the reaction. The prenylation of of 1,4-dihydroxy-2-naphthoate was also studied in a strain of E. coli which accumulates octaprenyl pyrophosphate, the natural precursor of the menaquinone side chain. The octaprenyltransferase was shown to be membrane bound and to require magnesium ions for optimal activity. A menA-mutant of E. coli was found to lack the octaprenyltransferase activity, suggesting that the menA gene is the structural gene for this enzyme. However, this strain had normal levels of 4-hydroxybenzoate octaprenyltransferase, the enzyme catalyzing the analogous prenylation reaction in ubiquinone biosynthesis, providing additional evidence that the two octaprenyltransferases are quite distinct.
据推测，1,4 - 二羟基 - 2 - 萘甲酸是大肠杆菌中甲基萘醌（维生素K2）生物合成过程中的萘中间体，八聚异戊二烯侧链从脱甲基甲基萘醌连接到该中间体上。在本研究中，在大肠杆菌的细胞提取物中证实了存在一种酶，即1,4 - 二羟基 - 2 - 萘甲酸八聚异戊二烯基转移酶，它催化1,4 - 二羟基 - 2 - 萘甲酸转化为脱甲基甲基萘醌。当萘甲酸盐与细胞提取物以及合成底物焦磷酸法呢酯在Triton X - 100存在下孵育时，会形成脱甲基甲基萘醌 - 9。焦磷酸单法呢酯不能替代反应中的焦磷酸。还在一种积累八聚异戊二烯焦磷酸（甲基萘醌侧链的天然前体）的大肠杆菌菌株中研究了1,4 - 二羟基 - 2 - 萘甲酸的异戊二烯基化。结果表明，八聚异戊二烯基转移酶与膜结合，并且需要镁离子以达到最佳活性。发现大肠杆菌的一个menA突变体缺乏八聚异戊二烯基转移酶活性，这表明menA基因是该酶的结构基因。然而，该菌株的4 - 羟基苯甲酸八聚异戊二烯基转移酶水平正常，该酶催化泛醌生物合成中的类似异戊二烯基化反应，这提供了额外的证据表明这两种八聚异戊二烯基转移酶是完全不同的。
