Konstantinova S G, Russanov E M
Department of Bioenergetics, Bulgarian Academy of Sciences, Sofia.
Comp Biochem Physiol B Biochem Mol Biol. 1996 Jan;113(1):125-30. doi: 10.1016/0305-0491(96)02008-1.
This paper presents data about the subcellular distribution of aconitases in rat liver and some properties of the aconitase activity in cytosol, mitochondria and soluble mitochondrial protein (SMP). The cytosolic and mitochondrial aconitase activity was 64.8% or 61.0% and 20.1% or 19.4% of the total rat liver aconitase activity when cis-aconitate or isocitrate was used as substrate. Aconitase activity of stored SMP and mitochondria with phosphate buffer (pH 7.4) and 0.25 M sucrose (pH 7.4) as isolation medium respectively, was reduced to an equal extent upon exposure to air. Fresh SMP preparations immediately and three hr after isolation had the same aconitase activity. It is concluded that phosphate has no role in the oxidative degradation of mitochondrial aconitase and does not inhibit it. Complete restoration of the decreased mitochondrial aconitase activity to the initial level was achieved with thiomalate and Fe2+ under anaerobic conditions or 60-70% was restored during the long period (60 min) of incubation with exogenous substrate. The aconitase activity of cytosol and mitochondria increased upon exposure to air for 7 1/2 hr. This finding is interpreted to suggest the existence of putative aconitase activity.
本文介绍了大鼠肝脏中乌头酸酶的亚细胞分布数据以及胞质溶胶、线粒体和可溶性线粒体蛋白（SMP）中乌头酸酶活性的一些特性。当以顺乌头酸或异柠檬酸作为底物时，胞质溶胶和线粒体的乌头酸酶活性分别占大鼠肝脏总乌头酸酶活性的64.8%或61.0%以及20.1%或19.4%。分别以磷酸盐缓冲液（pH 7.4）和0.25 M蔗糖（pH 7.4）作为分离介质储存的SMP和线粒体的乌头酸酶活性，在暴露于空气后均同等程度降低。新鲜的SMP制剂在分离后立即和三小时后的乌头酸酶活性相同。得出的结论是，磷酸盐在线粒体乌头酸酶的氧化降解中不起作用，也不抑制它。在厌氧条件下，用硫代苹果酸和Fe2+可使降低的线粒体乌头酸酶活性完全恢复到初始水平，或者在与外源底物长时间（60分钟）孵育期间可恢复60 - 70%。胞质溶胶和线粒体的乌头酸酶活性在暴露于空气7.5小时后增加。这一发现被解释为提示存在假定的乌头酸酶活性。
