Cejudo F J, Paneque A
J Bacteriol. 1986 Jan;165(1):240-3. doi: 10.1128/jb.165.1.240-243.1986.
Nitrate-grown Azotobacter chroococcum ATCC 4412 cells lack the ability to fix N2. Nitrogenase activity developed after the cells were suspended in a combined nitrogen-free medium and was paralleled by a concomitant decrease in nitrate assimilation capacity. In such treated cells exhibiting transitory nitrate assimilation and N2-fixation capacity, nitrate or nitrite caused a short-term inhibitory effect on nitrogenase activity which ceased once the anion was exhausted from the medium. The analog L-methionine-DL-sulfoximine, an inhibitor of glutamine synthetase, prevented inhibition of nitrogenase activity by nitrate or nitrite without affecting the uptake of these antions, which were reduced and stoichiometrically released into the external medium as ammonium. Inhibition of nitrogenase by nitrate (nitrite) did not take place in A. chroococcum MCD1, which is unable to assimilate either. We conclude that the short-term inhibitory effect of nitrate (nitrite) on nitrogenase activity is due to some organic product(s) formed during the assimilation of the ammonium resulting from nitrate (nitrite) reduction.
在硝酸盐培养基中生长的褐球固氮菌ATCC 4412细胞缺乏固氮能力。当细胞悬浮于无氮复合培养基中后，固氮酶活性得以产生，与此同时硝酸盐同化能力相应降低。在表现出短暂硝酸盐同化和固氮能力的此类处理细胞中，硝酸盐或亚硝酸盐会对固氮酶活性产生短期抑制作用，一旦培养基中的阴离子耗尽，这种抑制作用便会停止。谷氨酰胺合成酶抑制剂L-蛋氨酸-DL-亚砜亚胺可防止硝酸盐或亚硝酸盐对固氮酶活性的抑制，且不影响这些阴离子的吸收，这些阴离子会被还原并以铵的形式化学计量地释放到外部培养基中。硝酸盐（亚硝酸盐）对褐球固氮菌MCD1的固氮酶没有抑制作用，该菌株也无法同化硝酸盐（亚硝酸盐）。我们得出结论，硝酸盐（亚硝酸盐）对固氮酶活性的短期抑制作用是由于硝酸盐（亚硝酸盐）还原产生的铵同化过程中形成的某些有机产物所致。
