Galván A, Córdoba F, Cárdenas J, Fernández E
Departamento de Bioquímica y Biología Molecular y Fisiología, Facultad de Ciencias, Universidad de Córdoba, Spain.
Biochim Biophys Acta. 1991 May 24;1074(1):6-11. doi: 10.1016/0304-4165(91)90030-k.
Expression of nitrite uptake and nitrite reductase activities has been studied in Chlamydomonas reinhardtii under different nutritional conditions. Both activities were expressed at a low level in derepressed cells (with no nitrogen source) and at a high level in induced cells (with nitrate or nitrite). Nitrate was required for both activities to be maximally expressed. Ammonium-grown cells did not show nitrite uptake capability and had a basal nitrite reductase activity. Nitrite uptake but not nitrite reductase levels decreased very significantly in nitrate-induced cells subject to cycloheximide treatment, which suggests that protein(s) involved in the uptake are under a rapid turnover. Nitrite uptake expression was strongly inhibited by the presence of the glutamine synthetase inhibitor L-methionine-D,L-sulfoximine under either derepression or induction conditions, whereas that of nitrite reductase was not affected under the same conditions. Our results indicate that nitrite uptake expression is regulated primarily by ammonium, and that of nitrite reductase by both ammonium and ammonium derivative(s).
在不同营养条件下，对莱茵衣藻中亚硝酸盐摄取和亚硝酸还原酶活性的表达进行了研究。在去阻遏细胞（无氮源）中，这两种活性均低水平表达；而在诱导细胞（有硝酸盐或亚硝酸盐）中，这两种活性均高水平表达。两种活性要达到最大表达都需要硝酸盐。以铵盐培养的细胞不显示亚硝酸盐摄取能力，且具有基础亚硝酸还原酶活性。在经环己酰亚胺处理的硝酸盐诱导细胞中，亚硝酸盐摄取能力显著下降，但亚硝酸还原酶水平未受影响，这表明参与摄取的蛋白质周转迅速。在去阻遏或诱导条件下，谷氨酰胺合成酶抑制剂L-甲硫氨酸-D，L-亚砜亚胺的存在强烈抑制亚硝酸盐摄取的表达，而在相同条件下，亚硝酸还原酶的表达不受影响。我们的结果表明，亚硝酸盐摄取的表达主要受铵盐调节，而亚硝酸还原酶的表达则受铵盐及其衍生物调节。
