Guranowski A, Just G, Holler E, Jakubowski H
Katedra Biochemii, Akademia Rolnicza, Poznan, Poland.
Biochemistry. 1988 Apr 19;27(8):2959-64. doi: 10.1021/bi00408a044.
A novel way of enzymatic synthesis of diadenosine 5',5"'-P1,P4-tetraphosphate (AppppA), which does not involve aminoacyl-tRNA synthetases, has been discovered. Yeast AppppA alpha, beta-phosphorylase catalyzes irreversible conversion of adenosine 5'-phosphosulfate (APS) and ATP into AppppA according to the equation APS + ATP----AppppA + sulfate. In this reaction, the enzyme exhibits a broad pH optimum (between 6 and 8) and requires Mn2+, Mg2+, or Ca2+ ions for activity, with Mn2+ being twice as effective as Mg2+ or Ca2+ at optimal concentration (0.5 mM). The Km values computed for APS and ATP are 80 microM and 700 microM, respectively. The rate constant for the AppppA synthesis is 3 s-1 (pH 8.0, 30 degrees C, 0.5 mM MgCl2). Some ATP analogues like ppppA, GTP, adenosine 5'-(alpha, beta-methylenetriphosphate), and adenosine 5'-(beta, gamma-methylenetriphosphate), but not dATP, UTP, or CTP, are also substrates for AppppA phosphorylase and accept adenylate from APS with the formation of AppppA, AppppG, Appp(CH2)pA, and App(CH2)ppA, respectively. Functional versatility of yeast AppppA phosphorylase may provide a link between metabolism of AppppA on one hand and metabolism of APS and phosphate on the other and raises the possibility of participation of AppppA in regulation of metabolism of APS and/or inorganic phosphate in yeast.
已发现一种不涉及氨酰 - tRNA合成酶的二腺苷5',5"'-P1,P4 - 四磷酸（AppppA）的新型酶促合成方法。酵母AppppAα,β - 磷酸化酶根据方程式APS + ATP→AppppA + 硫酸盐，催化腺苷5'-磷酸硫酸酯（APS）和ATP不可逆转化为AppppA。在该反应中，该酶表现出较宽的pH最佳范围（6至8之间），并且活性需要Mn2 +、Mg2 +或Ca2 +离子，在最佳浓度（0.5 mM）下，Mn2 +的效果是Mg2 +或Ca2 +的两倍。计算得出的APS和ATP的Km值分别为80 microM和700 microM。AppppA合成的速率常数为3 s-1（pH 8.0，30℃，0.5 mM MgCl2）。一些ATP类似物如ppppA、GTP、腺苷5' - （α,β - 亚甲基三磷酸）和腺苷5' - （β,γ - 亚甲基三磷酸），但不是dATP、UTP或CTP，也是AppppA磷酸化酶的底物，并分别从APS接受腺苷酸形成AppppA、AppppG、Appp(CH2)pA和App(CH2)ppA。酵母AppppA磷酸化酶的功能多样性可能一方面在AppppA的代谢与另一方面APS和磷酸盐的代谢之间提供联系，并增加了AppppA参与酵母中APS和/或无机磷酸盐代谢调节的可能性。
