Roberts Scott J, Stewart Alan J, Sadler Peter J, Farquharson Colin
Roslin Institute, Roslin, Midlothian EH25 9PS, U.K.
Biochem J. 2004 Aug 15;382(Pt 1):59-65. doi: 10.1042/BJ20040511.
Human PHOSPHO1 is a phosphatase enzyme for which expression is upregulated in mineralizing cells. This enzyme has been implicated in the generation of P(i) for matrix mineralization, a process central to skeletal development. PHOSPHO1 is a member of the haloacid dehalogenase (HAD) superfamily of Mg2+-dependent hydrolases. However, substrates for PHOSPHO1 are, as yet, unidentified and little is known about its activity. We show here that PHOSPHO1 exhibits high specific activities toward phosphoethanolamine (PEA) and phosphocholine (PCho). Optimal enzymic activity was observed at approx. pH 6.7. The enzyme shows a high specific Mg2+-dependence, with apparent K(m) values of 3.0 microM for PEA and 11.4 microM for PCho. These results provide a novel mechanism for the generation of P(i) in mineralizing cells from PEA and PCho.
人磷酸酶1(PHOSPHO1)是一种磷酸酶,其在矿化细胞中的表达上调。该酶与基质矿化所需无机磷酸盐(P(i))的生成有关,而基质矿化是骨骼发育的核心过程。PHOSPHO1是依赖Mg2+的水解酶的卤代酸脱卤酶(HAD)超家族成员。然而,PHOSPHO1的底物尚未明确,其活性也知之甚少。我们在此表明,PHOSPHO1对磷酸乙醇胺(PEA)和磷酸胆碱(PCho)表现出高比活性。在约pH 6.7时观察到最佳酶活性。该酶表现出对Mg2+的高度依赖性,对PEA的表观K(m)值为3.0 microM,对PCho为11.4 microM。这些结果为从PEA和PCho在矿化细胞中生成P(i)提供了一种新机制。