Lorenz B, Batel R, Bachinski N, Müller W E, Schröder H C
Institut für Physiologische Chemie, Universität, Mainz, Germany.
Biochim Biophys Acta. 1995 Aug 17;1245(1):17-28. doi: 10.1016/0304-4165(95)00067-l.
Two exopolyphosphatases (exopolyphosphatase I and II; EC 3.6.1.11) which release orthophosphate from inorganic polyphosphates have been detected and purified for the first time from a marine sponge. Tethya lyncurium. Exopolyphosphatase I has a molecular mass of 45 kDa, a pH optimum of 5.0 and does not require divalent cations for activity, while exopolyphosphatase II has a molecular mass of 70 kDa, a pH optimum of 7.5 and displays optimal activity in the presence of Mg2+ ions. Final purification of the enzymes could be achieved by affinity chromatography on polyphosphate-modified zirconia. The mode of action of both enzymes was found to be processive. Orthophosphate is the sole product formed by exopolyphosphatase I, while degradation of linear polyphosphates by exopolyphosphatase II occurs to pyrophosphate as end product, which is hydrolyzed, if at all, only very slowly. Significant amounts of polyphosphate (approximately 30 micrograms/g wet weight) were found to be present in the sponge organism. Polyphosphate is shown to inhibit the formation of ATP by adenylate kinase activity present in T. lyncurium extracts in a competitive manner. The inhibitory effect of long-chain polyphosphates was higher than that of short-chain polyphosphate, suggesting a potential role of polyphosphate metabolism in regulating intracellular concentrations of adenylate nucleotides.
首次从海洋海绵Tethya lyncurium中检测并纯化出了两种能从无机多聚磷酸盐中释放正磷酸盐的外切多聚磷酸酶（外切多聚磷酸酶I和II；EC 3.6.1.11）。外切多聚磷酸酶I的分子量为45 kDa，最适pH为5.0，活性不需要二价阳离子；而外切多聚磷酸酶II的分子量为70 kDa，最适pH为7.5，在Mg2+离子存在时表现出最佳活性。通过在多聚磷酸盐修饰的氧化锆上进行亲和层析可实现酶的最终纯化。发现这两种酶的作用方式都是持续性的。正磷酸盐是外切多聚磷酸酶I形成的唯一产物，而外切多聚磷酸酶II对线性多聚磷酸盐的降解以焦磷酸作为终产物，焦磷酸即使会被水解，速度也非常缓慢。在海绵生物体中发现存在大量的多聚磷酸盐（约30微克/克湿重）。研究表明，多聚磷酸盐以竞争性方式抑制T. lyncurium提取物中腺苷酸激酶活性形成ATP。长链多聚磷酸盐的抑制作用高于短链多聚磷酸盐，这表明多聚磷酸盐代谢在调节细胞内腺苷酸核苷酸浓度方面可能发挥作用。
