Gbenle G O
Biochem Int. 1985 Feb;10(2):241-50.
The substrate specificity of a calcium-dependent endoribonuclease of Trypanosoma brucei cytoplasm has been further determined. The actions of the enzyme on transfer RNA, ribosomal RNA and various synthetic polyribonucleotides indicate that the enzyme degrades double-stranded as well as single-stranded RNAs; while it preferentially hydrolyses polyribonucleotides having adenylic acid residues, and has a pronounced preference for poly (adenylic acid). Its apparent Michaelis constant (Km) values using different substrates also suggest a base-preferential affinity of the enzyme to adenylate. The relative activity of the ribonuclease against homopolyribonucleotides is poly(A) greater than poly(U) greater than poly(C); while poly(G) is completely resistant to the activity. Poly(A) segments on poly(A)-rich RNA are selectively hydrolyzed by the endoribonuclease. A possible implication of this enzyme in the post-transcriptional modification and turnover of mRNA molecules is suggested.
布氏锥虫细胞质中一种钙依赖性核糖核酸内切酶的底物特异性已得到进一步确定。该酶对转运RNA、核糖体RNA和各种合成多聚核糖核苷酸的作用表明，它能降解双链和单链RNA；它优先水解具有腺苷酸残基的多聚核糖核苷酸，并且对聚（腺苷酸）有明显的偏好。使用不同底物时其表观米氏常数（Km）值也表明该酶对腺苷酸具有碱基优先亲和力。核糖核酸酶对同聚多聚核糖核苷酸的相对活性为聚（A）大于聚（U）大于聚（C）；而聚（G）对该活性完全有抗性。富含聚（A）的RNA上的聚（A）片段被核糖核酸内切酶选择性水解。提示了这种酶在mRNA分子转录后修饰和周转中的可能作用。
