STRUCTURAL ROLE OF DISULFIDE BRIDGES IN THE CYCLIC ADP-RIBOSE RELATED BIFUNCTIONAL ECTOENZYME CD38
STRUCTURAL ROLE OF DISULFIDE BRIDGES IN THE CYCLIC ADP-RIBOSE RELATED BIFUNCTIONAL ECTOENZYME CD38
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DOI：
10.1016/0014-5793(95)00715-l
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发表时间：
1995-07-24
期刊：
影响因子：
3.5
通讯作者：
DEFLORA, A
中科院分区：
文献类型：
--
作者：
GUIDA, L;FRANCO, L;DEFLORA, A
人CD 38是一种Ⅱ型细胞表面糖蛋白，是一种双功能胞外酶，催化ADP-核糖环化酶和环ADP-核糖（cADPR）水解酶反应。它的股份与环化酶从Aaplasia物种和定点诱变的研究最近已经证明了重要性，但没有阐明的作用，这些蛋白质之间的高度保守的几个半胱氨酸残基，N-乙基马来酰亚胺，碘乙酰胺和硫醇氧化剂未能影响环化酶或较弱的水解酶活性的Aaplasia californica蛋白。同样，这些试剂也不损害从人红细胞中纯化的CD 38的两种活性。β-巯基乙醇对Aaplasia酶活性没有影响，而它通过诱导其广泛的寡聚化而使CD 38的环化酶和cADPR水解酶失活。在完整的红细胞中，β-巯基乙醇依赖性酶失活完全通过预先用戊二醛交联膜蛋白来防止。这些数据表明，没有一个半胱氨酸残基在CD 38和失活蛋白中起任何直接催化作用，并且二硫键对于维持CD 38的单体催化活性结构是必需的。
Human CD38, a type II cell surface glycoprotein, is a bifunctional ectoenzyme catalyzing both ADP-ribosyl cyclase and cyclic ADP-ribose (cADPR) hydrolase reactions. It shares a high degree of sequence homology with the cyclase from Aplysia species and studies of site-directed mutagenesis have recently demonstrated the importance, but not elucidated the role, of several cysteine residues highly conserved between these proteins, N-Ethylmaleimide, iodoacetamide and thiol-oxidizing reagents failed to affect either the cyclase or the weaker hydrolase activity of the Aplysia califor nica protein. Likewise, these reagents did not impair the two activities of CD38 purified from human erythrocytes. beta-mercaptoethanol had no effect on the Aplysia enzyme activities, while it inactivated both the cyclase and the cADPR hydrolase of CD38 by inducing its extensive oligomerization. In intact erythrocytes the beta-mercaptoethanol-dependent enzyme inactivation was completely prevented by prior cross-linking of the membrane proteins with glutaraldehyde. These data demonstrate that none of the cysteine residues plays any direct catalytic role in CD38 and Aplysia proteins, and that disulfide bridges are essential for maintaining the monomeric, catalytically active structure of CD38.