Kinetic competence of the cADP-ribose-CD38 complex as an intermediate in the CD38/NAD+ glycohydrolase-catalysed reactions:: implication for CD38 signalling
Kinetic competence of the cADP-ribose-CD38 complex as an intermediate in the CD38/NAD+ glycohydrolase-catalysed reactions:: implication for CD38 signalling
复制标题
DOI：
10.1042/bj3580399
复制
发表时间：
2001-09-01
影响因子：
4.1
通讯作者：
Schuber, F
中科院分区：
文献类型：
--
作者：
Cakir-Kiefer, I;Muller-Steffner, H;Schuber, F
CD 38/NAD（+）糖水解酶是一种II型跨膜糖蛋白，广泛用于研究T细胞和B细胞的活化和分化。CD 38具有两种不同的活性：它是一种信号转导分子和一种胞外酶，可将NAD（+）转化为ADP-核糖（NAD（+）糖水解酶活性）和小比例的cADP-核糖（cADPR; ADP-核糖基环化酶活性），这是一种钙动员代谢产物，最终也可被水解（cADPR水解酶活性）。这两种性质之间的关系，以及在游离或酶复合的cADPR形成中对信号传导的显著要求，仍然不明确。在本研究中，我们想测试CD 38-cADPR复合物是否在NAD（+）转化为反应产物ADP-核糖的动力学能力。原则上，这种复合物可以通过构象变化与CD 38的相邻配偶体进行串扰，从而触发信号传导现象。对CD 38/NAD（+）糖水解酶催化的2 '-脱氧-2'-氨基核糖-NAD（+）和ADP-环[N1，C1 ']-2'-脱氧-2 '-氨基核糖（分别为NAD（+）和cADPR的缓慢水解类似物）的水解测量的动力学参数分析排除了CD 38-cADPR复合物可以在稳态条件下积累。这一点通过模拟CD 38的普遍动力学机制得到了证实，该机制涉及一个共同的E . ADP-核糖基在酶催化反应产物形成中的中间体。利用这种机制，发现了将NAD（+）糖水解酶转化为ADP-核糖基环化酶的微观速率条件。总之，目前的工作表明，如果与合作伙伴的串扰依赖于CD 38的构象变化，这是最有可能不归因于CD 38-cADPR复合物的形成。与最近关于由CD 38配体触发的构象变化的结果一致[Berthelier，Laboureau，Boulla，Schuber和Deterre（2000）Eur. J.Biochem.267，3056-3064]，我们认为Michaelis CD 38-NAD（+）复合物可以替代地发挥这样的作用。
CD38/NAD(+) glycohydrolase is a type II transmembrane glycoprotein widely used to study T- and B-cell activation and differentiation. CD38 is endowed with two different activities: it is a signal transduction molecule and an ectoenzyme that converts NAD(+) into ADP-ribose (NAD(+) glycohydrolase activity) and small proportions of cADP-ribose (cADPR; ADP-ribosyl cyclase activity), a calcium-mobilizing metabolite, which, ultimately, can also be hydrolysed (cADPR hydrolase activity). The relationship between these two properties, and strikingly the requirement for signalling in the formation of free or enzyme-complexed cADPR, is still ill-defined. In the present study we wanted to test whether the CD38-cADPR complex is kinetically competent in the conversion of NAD(+) into the reaction product ADP-ribose. In principle, such a complex could be invoked for cross-talk, via conformational changes, with neighbouring partner(s) of CD38 thus triggering the signalling phenomena. Analysis of the kinetic parameters measured for the CD38/NAD(+) glycohydrolase-catalysed hydrolysis of 2'-deoxy-2'-aminoribo-NAD(+) and ADP-cyclo[N1,C1']-2'-deoxy-2'-aminoribose (slowly hydrolysable analogues of NAD(+) and cADPR respectively) ruled out that the CD38-cADPR complex can accumulate under steady-state conditions. This was borne out by simulation of the prevalent kinetic mechanism of CD38, which involve the partitioning of a common E . ADP-ribosyl intermediate in the formation of the enzyme-catalysed reaction products. Using this mechanism, microscopic rate conditions were found which transform a NAD(+) glycohydrolase into an ADP-ribosyl cyclase. Altogether, the present work shows that if the cross-talk with a partner depends on a conformational change of CD38, this is most probably not attributable to the formation of the CD38-cADPR complex. In line with recent results on the conformational change triggered by CD38 ligands [Berthelier, Laboureau, Boulla, Schuber and Deterre (2000) Eur. J. Biochem. 267, 3056-3064], we believe that the Michaelis CD38-NAD(+) complex could play such a role instead.