Gbenle G O
Mol Biochem Parasitol. 1985 Apr;15(1):37-47. doi: 10.1016/0166-6851(85)90027-1.
An endoribonuclease and an exoribonuclease have been isolated simultaneously from the cytoplasm of Trypanosoma brucei by hydroxyapatite column chromatography. The endoribonuclease produced oligonucleotides from poly(adenylic acid) with 5'-phosphate and 3'-OH termini. The exoribonuclease produced only ribonucleoside 5'-phosphates from poly(adenylic acid). The relative rates of degradation of synthetic homopolynucleotides by the endoribonuclease under standard conditions were in the order poly(adenylic acid) greater than poly(uridylic acid) poly(cytidylic acid); for the exoribonuclease the order was poly(adenylic acid) poly(uridylic acid) greater than poly(cytidylic acid). Natural transfer and ribosomal RNAs were also degraded by both enzymes, while DNA was resistant to them. The optimal pH of activity for each enzyme was 7.5-8.0. Both ribonucleases require Ca2+ for maximum enzymatic activity.
通过羟基磷灰石柱色谱法，从布氏锥虫的细胞质中同时分离出一种核糖核酸内切酶和一种核糖核酸外切酶。核糖核酸内切酶从聚腺苷酸产生具有5'-磷酸和3'-羟基末端的寡核苷酸。核糖核酸外切酶从聚腺苷酸仅产生核糖核苷5'-磷酸。在标准条件下，核糖核酸内切酶对合成同聚核苷酸的相对降解速率顺序为聚腺苷酸＞聚尿苷酸＞聚胞苷酸；对于核糖核酸外切酶，顺序为聚腺苷酸＞聚尿苷酸＞聚胞苷酸。天然转移RNA和核糖体RNA也被这两种酶降解，而DNA对它们有抗性。每种酶的最佳活性pH为7.5 - 8.0。两种核糖核酸酶都需要Ca2+以达到最大酶活性。
