Weissman G S
Department of Biology, Rutgers University, Camden, New Jersey 08102.
Plant Physiol. 1972 Feb;49(2):142-5. doi: 10.1104/pp.49.2.142.
Total pyridine nucleotide concentration of root tissue for young soybean (Glycine max var. Bansei) and sunflower (Helianthus annuus L. var. Mammoth Russian) plants is the same with either ammonium or nitrate, but nitrate results in an increased proportion of total oxidized plus reduced NADP (NADP[H]) seemingly at the expense of NAD. The activity of NADH- and NADPH-dependent forms of glutamic acid dehydrogenase is correlated with the ratio of total oxidized plus reduced NAD to NADP(H). The low NAD: NADH ratio maintained in nitrate roots despite active NADH utilization via nitrate reductase and glutamic acid dehydrogenase may be the result of nitrate-stimulated glycolysis. Nitrate roots also maintain a high level of NADPH, presumably by the stimulatory effect of nitrate utilization on glucose-6-phosphate dehydrogenase activity. In the presence of nitrate rather than ammonium, the highly active nitrate-reducing leaves of soybean show a greater proportion of total pyridine nucleotide in the form of NADP(H) than do the inactive leaves of sunflower.For all tissues examined, ammonium nutrition yields a higher concentration of total adenine nucleotide than is found with nitrate. The data indicate the production of a higher level of metabolites that enter into purine synthesis with ammonium than with nitrate. Glutamine synthetase activity can be correlated with the concept that enzymes utilizing ATP for biosynthetic purposes increase in activity in accordance with the energy level of the cell.
对于幼嫩的大豆（Glycine max var. Bansei）和向日葵（Helianthus annuus L. var. Mammoth Russian）植株，其根系组织中的总吡啶核苷酸浓度在以铵盐或硝酸盐为氮源时是相同的，但硝酸盐会导致总氧化型加还原型NADP（NADP[H]）的比例增加，这似乎是以NAD为代价的。依赖NADH和NADPH的谷氨酸脱氢酶活性与总氧化型加还原型NAD与NADP（H）的比例相关。尽管通过硝酸还原酶和谷氨酸脱氢酶对NADH有活跃的利用，但硝酸盐处理的根系中维持的低NAD:NADH比例可能是硝酸盐刺激糖酵解的结果。硝酸盐处理的根系也维持着高水平的NADPH，这可能是由于硝酸盐利用对葡萄糖-6-磷酸脱氢酶活性的刺激作用。在以硝酸盐而非铵盐为氮源时，大豆中高活性的硝酸还原叶片中以NADP（H）形式存在的总吡啶核苷酸比例比向日葵中无活性的叶片更高。对于所有检测的组织，铵营养比硝酸盐营养产生更高浓度的总腺嘌呤核苷酸。数据表明，与硝酸盐相比，铵盐能产生更高水平的参与嘌呤合成的代谢物。谷氨酰胺合成酶活性与这样的概念相关，即利用ATP进行生物合成的酶的活性会根据细胞的能量水平而增加。
