产品内容
本酶催化的反应为(1) (Ribonucleotide)n-3'-Phosphate + 5'-Hydroxy-(Ribonucleotide)m + GTP = (Ribonucleotide)n+m + GMP + Diphosphate (Overall Reaction);;(1a) GTP + [RNA Ligase]-L-Histidine = [RNA Ligase]-Ntau-(5'-Guanosyl-Phosphono)-L-Histidine + Diphosphate;;(1b) [RNA Ligase]-Ntau-(5'-Guanosyl-Phosphono)-L-Histidine + (Ribonucleotide)n-3'-Phosphate = (Ribonucleotide)n-3'-(5'-Diphosphoguanosine) + [RNA Ligase]-L-Histidine;;(1c) (Ribonucleotide)n-3'-(5'-Diphosphoguanosine) + 5'-Hydroxy-(Ribonucleotide)m = (Ribonucleotide)n+m + GMP;;(2) (Ribonucleotide)n-2',3'-Cyclophosphate + 5'-Hydroxy-(Ribonucleotide)m + GTP + H2O = (Ribonucleotide)n+m + GMP + Diphosphate (Overall Reaction);;(2a) (Ribonucleotide)n-2',3'-Cyclophosphate + H2O = (Ribonucleotide)n-3'-Phosphate;;(2b) GTP + [RNA Ligase]-L-Histidine = [RNA Ligase]-Ntau-(5'-Guanosyl-Phosphono)-L-Histidine + Diphosphate;;(2c) [RNA Ligase]-Ntau-(5'-Guanosyl-Phosphono)-L-Histidine + (Ribonucleotide)n-3'-Phosphate = (Ribonucleotide)n-3'-(5'-Diphosphoguanosine) + [RNA Ligase]-L-Histidine;;(2d) (Ribonucleotide)n-3'-(5'-Diphosphoguanosine) + 5'-Hydroxy-(Ribonucleotide)m = (Ribonucleotide)n+m + GMP，系统名称为Poly(ribonucleotide)-3'-Phosphate:5'-Hydroxy-Poly(ribonucleotide) Ligase (GMP-Forming)，该酶是一种依赖 GTP 和 Mn2+ 的 3'-5' 核酸连接酶，能够将带有 3'-磷酸或 2',3'-环磷酸末端的 RNA 与带有 5'-羟基末端的 RNA 连接起来。只要 DNA 末端未配对，它也可以将带有 3'-磷酸末端的 DNA 与带有 5'-羟基末端的 DNA 连接 [6]。该酶存在于生命三界的成员中，对后生动物中含内含子 tRNA 的剪接至关重要。该反应遵循三步机制：首先通过 GTP 水解活化酶，在鸟苷酸与一个组氨酸残基之间形成磷酰胺键。鸟苷酸基团随后被转移到底物的 3'-磷酸末端，形成带帽结构 [DNA/RNA]-3'-(5'-二磷酸鸟苷)。当有合适的 5'-OH 末端时，该酶催化 5'-OH 进攻带帽末端，形成 3'-5' 磷酸二酯剪接连接点并释放鸟苷酸。当作用于 RNA 2',3'-环磷酸时，该酶还催化一个额外反应，将环磷酸水解为 3'-磷酸 [9]。后生动物的酶需要活化辅因子才能实现多轮转换催化 [8]。
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