Steinkühler C, Sapora O, Carrì M T, Nagel W, Marcocci L, Ciriolo M R, Weser U, Rotilio G
Department of Biology, University of Rome, Tor Vergata, Italy.
J Biol Chem. 1991 Dec 25;266(36):24580-7.
Cu,Zn-superoxide dismutase activity, expressed on the basis of cell number, increased by 50% during sodium butyrate-induced differentiation of human K562 erythroleukemia cells. The increased enzyme activity was found to be concomitant with constant Cu,Zn-superoxide dismutase mRNA and immunoreactive protein levels and was accompanied by a rise in intracellular copper and glutathione. Incubation of K562 cell homogenates with copper caused an increase of Cu,Zn-superoxide dismutase activity which reached the levels observed after differentiation in the presence of sodium butyrate. The same treatment led to no significant activity increase in homogenates derived from differentiated cells. Externally added ceruloplasmin increased both intracellular copper levels and Cu,Zn-superoxide dismutase activity in undifferentiated cells to a level comparable with that observed after induction of differentiation. Both increments were abolished by depletion of cell glutathione. Cu,Zn-superoxide dismutase purified from control cells had both a lower kcat and a lower copper content than the enzyme purified from differentiated cells. From these data we conclude that: 1) Cu,Zn-superoxide dismutase is present in K562 cells also under the form of a less active copper-deficient enzyme, 2) the extent of enzyme activation is regulated post-translationally by differential delivery of copper as a function of differentiation stage, and 3) glutathione is likely to play a role in delivering copper to the copper-deficient protein in intact K562 cells.
以细胞数量为基础表示的铜锌超氧化物歧化酶活性，在丁酸钠诱导人K562红白血病细胞分化过程中增加了50%。发现酶活性增加与铜锌超氧化物歧化酶mRNA和免疫反应性蛋白水平恒定相伴，并伴随着细胞内铜和谷胱甘肽的增加。用铜孵育K562细胞匀浆导致铜锌超氧化物歧化酶活性增加，达到在丁酸钠存在下分化后观察到的水平。相同处理导致分化细胞来源的匀浆中活性没有显著增加。外部添加的铜蓝蛋白使未分化细胞内的铜水平和铜锌超氧化物歧化酶活性都增加到与诱导分化后观察到的水平相当。细胞谷胱甘肽耗尽消除了这两种增加。从对照细胞纯化的铜锌超氧化物歧化酶与从分化细胞纯化的酶相比，其催化常数和铜含量都较低。从这些数据我们得出结论：1）铜锌超氧化物歧化酶在K562细胞中也以活性较低的缺铜酶形式存在；2）酶激活程度在翻译后由作为分化阶段函数的铜的差异递送调节；3）谷胱甘肽可能在完整K562细胞中将铜递送至缺铜蛋白中发挥作用。
