产品内容
本酶催化的反应为GTP + [RNA]-3'-(3'-Phospho-Ribonucleoside) = GMP + Diphosphate + [RNA]-3'-(2',3'-Cyclophospho)-Ribonucleoside (Overall Reaction);;(1a) GTP + [RNA 3'-Phosphate Cyclase]-L-Histidine = 5'-Guanosyl [RNA 3'-Phosphate Cyclase]-Ntau-Phosphono-L-Histidine + Diphosphate;;(1b) 5'-Guanosyl [RNA 3'-Phosphate Cyclase]-Ntau-Phosphono-L-Histidine + [RNA]-3'-(3'-Phospho-Ribonucleoside) = [RNA 3'-Phosphate Cyclase]-L-Histidine + [RNA]-3'-Ribonucleoside-3'-(5'-Diphosphoguanosine);;(1c) [RNA]-3'-Ribonucleoside-3'-(5'-Diphosphoguanosine) = [RNA]-3'-(2',3'-Cyclophospho)-Ribonucleoside + GMP，系统名称为RNA-3'-Phosphate:RNA Ligase (Cyclizing, GMP-Forming)，该酶对GTP具有专一性，已从古菌激烈火球菌 Pyrococcus furiosus 中得到表征。该酶在依赖GTP的反应中将各种RNA底物的3'-末端磷酸转化为2',3'-环磷酸二酯。催化按三步机制进行：首先GTP激活酶，在鸟苷酸与一个组氨酸残基之间形成磷酰胺键；随后鸟苷酸基团转移到底物的3'-磷酸末端，形成加帽结构 [RNA]-3'-(5'-二磷酸鸟苷)；最后该酶催化邻位O-2'进攻3'-磷原子，形成环磷酸并释放鸟苷酸。参见 EC 6.5.1.4，RNA 3'-末端磷酸环化酶（ATP）。
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