MODE OF ACTION OF POLY(ADP-RIBOSE) GLYCOHYDROLASE
MODE OF ACTION OF POLY(ADP-RIBOSE) GLYCOHYDROLASE
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DOI：
10.1016/0167-4781(94)90058-2
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发表时间：
1994-10-18
期刊：
影响因子：
--
通讯作者：
POIRIER, GG
中科院分区：
文献类型：
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作者：
BROCHU, G;DUCHAINE, C;POIRIER, GG
ADP-核糖均聚物的周转（已知参与许多 DNA 相关功能）由 2 个主要酶控制。聚(ADP-核糖)聚合酶(EC 2.4.2.30)从NAD合成聚合物，并且聚(ADP-核糖)糖水解酶(PARG)是负责其分解代谢的主要酶(Thomassin等人(1992)Biochim.Biophys.Acta 1137, 171-181)。在体内，聚（ADP-核糖）聚合物构成支化聚合物的异质群体，其大小为200-400个残基。它们被 PARG 快速降解，显示出作为聚合物尺寸函数的可变动力学参数。多项研究表明，PARG 对其底物以外切糖苷方式起作用，但其他研究则观察到它可以以内切/外切糖苷方式起作用。我们使用HPLC纯化的长游离聚合物和非常纯的PARG，在最适合表达PARG所有活性的条件下分析了PARG的作用模式。我们最终表明，在大的游离聚合物上，PARG 表现出糖苷内切活性和糖苷外切活性。这种糖苷内切活性可能在细胞对 DNA 损伤的反应中发挥重要作用。
The turnover of the homopolymer of ADP-ribose, which is known to be involved in many DNA-related functions, is controlled by 2 principal enzymes. Poly(ADP-ribose) polymerase (EC 2.4.2.30) synthesizes the polymer from NAD, and poly(ADP-ribose) glycohydrolase (PARG) is the major enzyme responsible for its catabolism (Thomassin et al. (1992) Biochim. Biophys. Acta 1137, 171-181). In vivo, poly(ADP-ribose) polymers constitute a heterogeneous population of branched polymers attaining sizes of 200-400 residues. They are rapidly degraded by PARG, displaying variable kinetic parameters as a function of polymer size. Several studies have suggested that PARG acts exoglycosidically on its substrate but others observed that it could act endo/exo-glycosidically. We analysed the mode of action of PARG under conditions most suitable for expression of all the activities of PARG, using HPLC purified long free polymer and very pure PARG. We conclusively show that on large free polymers, PARG exhibits endoglycosidic activity along with exoglycosidic activity. This endoglycosidic activity could have a significant role during cellular response to DNA damage.