Das M K, Vithayathil P J
Int J Pept Protein Res. 1978 Nov;12(5):242-8. doi: 10.1111/j.1399-3011.1978.tb02894.x.
The susceptibility of a monodeamidated RNAaseA (RNAaseAa1) towards carboxypeptidaseA , alpha-chymotrypsin and pepsin has been studied. Similar to RNAaseA, the C-terminal of RNAaseAa1 is not available for carboxypeptidaseA hydrolysis. The thermal stability of RNAaseAa1 as probed through chymotryptic digestion is found to be less than that of RNAaseA. Preliminary chromatographic analysis of the digested material, however, suggests that the nature of thermal transition might be the same in the two proteins. Pepsin inactivates RNAaseAa1 more slowly than does RNAaseA. Accordingly, less peptide bonds, almost half that of RNAaseA, are cleaved by pepsin in RNAaseAa1. The accumulation of RNAase-P type intermediates is not evident during peptic digestion of RNAaseAa1. Reaction with O-benzoquinone at low pH shows that methionines of the deamidated protein seem to have higher reactivities. These observations indicate a different structure for RNAaseAa1 at elevated temperature and low pH.
已对单脱酰胺核糖核酸酶A（核糖核酸酶Aa1）对羧肽酶A、α-胰凝乳蛋白酶和胃蛋白酶的敏感性进行了研究。与核糖核酸酶A相似，核糖核酸酶Aa1的C末端不可用于羧肽酶A水解。通过胰凝乳蛋白酶消化检测到的核糖核酸酶Aa1的热稳定性低于核糖核酸酶A。然而，对消化产物的初步色谱分析表明，两种蛋白质的热转变性质可能相同。胃蛋白酶使核糖核酸酶Aa1失活的速度比核糖核酸酶A慢。因此，胃蛋白酶在核糖核酸酶Aa1中切割的肽键较少，几乎是核糖核酸酶A的一半。在核糖核酸酶Aa1的胃蛋白酶消化过程中，核糖核酸酶-P型中间体的积累不明显。在低pH下与邻苯醌反应表明，脱酰胺蛋白的甲硫氨酸似乎具有更高的反应活性。这些观察结果表明，核糖核酸酶Aa1在高温和低pH下具有不同的结构。
