Herrero A, Flores E, Guerrero M G
Arch Biochem Biophys. 1984 Nov 1;234(2):454-9. doi: 10.1016/0003-9861(84)90292-3.
The in vivo stability of ferredoxin-nitrate reductase from the cyanobacterium Anacystis nidulans under conditions of inhibited protein synthesis has been studied in nitrate-grown cells. A light-promoted rapid decay in cellular nitrate reductase activity took place in the absence of any added nitrogen source, but not in the presence of nitrate, nitrite, or ammonium. The inactivation process seemed to proceed in two sequential steps. The first step required both light and oxygen, and was inhibited by 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) or, to a lesser extent, by sulfhydryl-containing compounds. The resulting inactive form of nitrate reductase, apparently suffering from an oxidative modification, could be reactivated in vivo either by switching-off the light or by addition of inorganic nitrogenous compounds. Prolonged illumination of the cells in the absence of a nitrogen source led to further modification of the enzyme, which could not be reversed. Stability of the active enzyme appears to be a decisive factor contributing to the determination of the actual level of nitrate reductase in A. nidulans cells.
已在硝酸盐培养的细胞中研究了来自蓝细菌集胞藻6803的铁氧化还原蛋白-硝酸还原酶在蛋白质合成受抑制条件下的体内稳定性。在没有添加任何氮源的情况下，细胞硝酸还原酶活性会发生光促进的快速衰减，但在存在硝酸盐、亚硝酸盐或铵的情况下则不会。失活过程似乎分两个连续步骤进行。第一步需要光和氧气，并且受到3-(3,4-二氯苯基)-1,1-二甲基脲（DCMU）的抑制，或者在较小程度上受到含巯基化合物的抑制。由此产生的硝酸还原酶失活形式显然遭受了氧化修饰，通过关闭光照或添加无机含氮化合物可在体内重新激活。在没有氮源的情况下对细胞进行长时间光照会导致酶的进一步修饰，这种修饰无法逆转。活性酶的稳定性似乎是决定集胞藻6803细胞中硝酸还原酶实际水平的一个决定性因素。
