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World J Microbiol Biotechnol. 1996 May;12(3):285-7. doi: 10.1007/BF00360929.
Nitrate uptake and nitrite efflux patterns in Nostoc MAC showed a rapid phase followed by their saturation. Nitrite efflux was maximum in nitrate medium whereas the cells incubated in N2 and NH 4 (+) media exhibited a decreased nitrite efflux activity. The simultaneous presence of NH 4 (+) and nitrate significantly decreased nitrite efflux. L-Methionine-DL-sulphoximine (MSX) prevented inhibition of nitrite efflux by NH 4 (+) . In the dark there was negligible nitrite efflux, whereas illumination increased the rate of nitrite efflux significantly. The nitrite efflux system was maximally operative at pH 8.0, 30°C and a photon fluence rate of 50 μmol m(-2). s(-1). These results confirm that (i) the nitrite efflux system in Nostoc MAC is dependent upon nitrate uptake and assimilation and is repressible by NH 4 (+) ; (ii) NH 4 (+) itself is not the actual repressor of nitrite efflux; a product of NH 4 (+) assimilation via glutamine synthetase (GS) is required for repression to occur; (iii) the catalytic function of GS does not appear to be involved in nitrate assimilation-dependent nitrite efflux, and (iv) the optimum pH, temperature and illumination for maximum nitrite efflux were found to be 8.0, 30°C and 50μmol m(-2). s respectively.
硝酸根吸收和亚硝酸盐的排出模式在念珠藻 MAC 中表现为一个快速阶段，随后是它们的饱和阶段。在硝酸盐培养基中，亚硝酸盐的排出量最大，而在 N2 和 NH4 (+) 培养基中培养的细胞则表现出降低的亚硝酸盐排出活性。同时存在 NH4 (+) 和硝酸盐会显著降低亚硝酸盐的排出。L-蛋氨酸-DL-亚砜亚胺 (MSX) 可以防止 NH4 (+) 对亚硝酸盐排出的抑制。在黑暗中，亚硝酸盐的排出可以忽略不计，而光照则显著增加了亚硝酸盐的排出速率。亚硝酸盐排出系统在 pH8.0、30°C 和 50μmol m(-2). s(-1) 的光量子通量率下达到最大活性。这些结果证实：（i）念珠藻 MAC 中的亚硝酸盐排出系统依赖于硝酸盐的吸收和同化，并且可以被 NH4 (+) 抑制；（ii）NH4 (+) 本身不是亚硝酸盐排出的实际抑制剂；通过谷氨酰胺合成酶 (GS) 同化 NH4 (+) 需要一种产物才能发生抑制；（iii）GS 的催化功能似乎不参与硝酸盐同化依赖的亚硝酸盐排出；（iv）最大亚硝酸盐排出的最佳 pH 值、温度和光照分别为 8.0、30°C 和 50μmol m(-2). s。
