Kouretas D, Antonoglou O
Laboratory of Pharmacology, School of Veterinary Medicine, University of Thessaly, Karditsa, Greece.
Cell Mol Biol (Noisy-le-grand). 1997 Dec;43(8):1181-90.
Four, widely used, ribonucleases were found to protect their substrates from acid precipitation by causing, evidently, a modification of their physicochemical properties. The protection was dependent on the kind of substrate while the ratio of protective to nucleolytic activity varied widely between the four enzymes. The protection was enhanced by some nucleotides like UMP, CMP and IMP and decreased in the presence of several bivalent ions like Zn++, Co++ and Cu++. It was completely abolished when the substrates were hybridized with their complementary ribohomopolymers. In the case of bovine pancreatic ribonuclease, the part of the molecule which was responsible for the protective activity was localized on the enzyme domain characterized as S-protein, which lacks nucleolytic activity. The observed property of ribonucleases could lead to false data when the measurement of TCA-soluble material is the method used to follow the purification of ribonucleases or to study their activity. It was also found that ribonuclease S-protein enhances the catalytic activity of B. Cereus RNAse. S-protein could potentiate other RNAses activity like onconase, which has recently been used as an anticancer agent.
发现四种广泛使用的核糖核酸酶可通过明显改变其底物的物理化学性质来保护它们免受酸沉淀的影响。这种保护作用取决于底物的种类，而四种酶的保护活性与核酸分解活性的比例差异很大。一些核苷酸如UMP、CMP和IMP可增强这种保护作用，而在几种二价离子如Zn++、Co++和Cu++存在时，保护作用会减弱。当底物与其互补的核糖均聚物杂交时，这种保护作用会完全消失。就牛胰核糖核酸酶而言，负责保护活性的分子部分位于被称为S蛋白的酶结构域上，该结构域缺乏核酸分解活性。当使用测量三氯乙酸可溶性物质的方法来跟踪核糖核酸酶的纯化或研究其活性时，核糖核酸酶的这种特性可能会导致错误的数据。还发现核糖核酸酶S蛋白可增强蜡状芽孢杆菌核糖核酸酶的催化活性。S蛋白可增强其他核糖核酸酶的活性，如最近被用作抗癌剂的癌酶。
