Baudhuin P, Peeters-Joris C, Bartholeyns J
Eur J Biochem. 1975 Sep 1;57(1):213-20. doi: 10.1111/j.1432-1033.1975.tb02293.x.
Six types of nuclease activities were found to be concentrated in the large granule fraction isolated from rat liver homogenastes by differential centrifugation. Analysis by density equilibration shows that three nucleases are associated with mitochondria: an alkaline ribonulcease (pH optimum 8.8), an alkaline deoxyribonuclease (pH optimum 7.6) and an enzyme acting on polyriboadenylate (pH optimum 7.5). When the outer mitochondrial membrane is ruptured in hypotonic medium, the three mitochondrial nucleases are partially solubilized. Solubilization is however obtained by addition of KCL to the suspension medium. It is concluded that mitochondrial nucleases are localized in the intermembrane space but that an adsorption to the outer face of the inner mitochondrial membrane occurs in sucrose 0.25 M. The mitochondrial localization of alkaline ribonuclease, alkaline deoxyribonuclease and polyadenylate accounts for at least 80% of the activity of liver homogenate; nevertheless, an excess of these enzymes is present in the microsomal fraction. Although no definite conculusion can be reached for the significance of this observation, it is shown by density equilibration analysis that these nuclease are not associated either with ribosomes or with the membranes which are the major component of the microsomal fraction.
通过差速离心从大鼠肝脏匀浆中分离出的大颗粒部分中发现有六种核酸酶活性。密度平衡分析表明，三种核酸酶与线粒体相关：一种碱性核糖核酸酶（最适pH 8.8）、一种碱性脱氧核糖核酸酶（最适pH 7.6）和一种作用于聚核糖腺苷酸的酶（最适pH 7.5）。当线粒体外膜在低渗介质中破裂时，这三种线粒体核酸酶会部分溶解。然而，通过向悬浮介质中添加氯化钾可实现溶解。得出的结论是，线粒体核酸酶定位于膜间隙，但在0.25M蔗糖中会吸附到线粒体内膜的外表面。碱性核糖核酸酶、碱性脱氧核糖核酸酶和聚腺苷酸的线粒体定位至少占肝脏匀浆活性的80%；然而，微粒体部分中存在过量的这些酶。尽管对于这一观察结果的意义无法得出明确结论，但密度平衡分析表明，这些核酸酶既不与核糖体相关，也不与作为微粒体部分主要成分的膜相关。
