Elson M, Glitz D G
Biochemistry. 1975 Apr 8;14(7):1471-6. doi: 10.1021/bi00678a019.
An alkaline ribonuclease (pH optimum near 8) has been purified from whole beef brains and found to have a base specificity like that of bovine pancreatic ribonuclease, but in most other respects to be distinguishable from the enzymes of bovine pancreas, semen, or brain nuclei. The preparation appears homogeneous in sedimentation equilibrium and probably so in polyacrylamide gel electrophoresis under normal or dissociating conditions. Sedimentation equilibrium and SDS gel electrophoresis both indicate a molecular weight of 2.4-2.6 times 10-4, and tryptic and chymotrypic peptide patterns are consistent with a protein of this size. No dissociation into subunits has been attained. The enzyme is not precipitated by antiserum to pancreatic ribonuclease, although its activity is inhibited by this antiserum with low efficiency. In comparisons of the hydrolysis of RNA the brain enzyme was found to have a similar specificity to pancreatic RNase, but to have a loser Km for RNA and to produce significantly different oligonucleotides upon partial hydrolysis of bacteriophage RNA, suggesting differences in the mechanism of substrate recognition. In contrast, nuclease inactivation by iodoacetate at pH 5.5 is indistinguishable for pancreatic or purified brain RNase.
一种碱性核糖核酸酶（最适pH接近8）已从全牛脑中纯化出来，发现其碱基特异性与牛胰核糖核酸酶相似，但在大多数其他方面与牛胰腺、精液或脑细胞核中的酶不同。该制剂在沉降平衡中显得均一，在正常或解离条件下的聚丙烯酰胺凝胶电泳中可能也是如此。沉降平衡和SDS凝胶电泳均表明分子量为2.4 - 2.6×10⁴，胰蛋白酶和胰凝乳蛋白酶肽图谱与这种大小的蛋白质一致。尚未实现亚基解离。该酶不会被抗胰核糖核酸酶抗血清沉淀，尽管其活性会被这种抗血清低效抑制。在RNA水解的比较中，发现脑酶与胰核糖核酸酶具有相似的特异性，但对RNA的Km值更低，并且在噬菌体RNA部分水解时产生明显不同的寡核苷酸，这表明底物识别机制存在差异。相比之下，在pH 5.5时碘乙酸对胰核糖核酸酶或纯化脑核糖核酸酶的失活作用没有区别。
