Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.7.1.4 (nitrite reductase)
 1,847 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An NADPH-dependent NO2--reducing system was reconstituted in vitro using ferredoxin (Fd) NADP+ oxidoreductase (FNR), Fd, and nitrite reductase (NiR) from the green alga Chlamydomonas reinhardtii. NO2- reduction was dependent on all protein components and was operated under either aerobic or anaerobic conditions. NO2- reduction by this in vitro pathway was inhibited up to 63% by 1 mm NADP+. NADP+ did not affect either methyl viologen-NiR or Fd-NiR activity, indicating that inhibition was mediated through FNR. When NADPH was replaced with a glucose-6-phosphate dehydrogenase (G6PDH)-dependent NADPH-generating system, rates of NO2- reduction reached approximately 10 times that of the NADPH-dependent system. G6PDH could be replaced by either 6-phosphogluconate dehydrogenase or isocitrate dehydrogenase, indicating that G6PDH functioned to: (a) regenerate NADPH to support NO2- reduction and (b) consume NADP+, releasing FNR from NADP+ inhibition. These results demonstrate the ability of FNR to facilitate the transfer of reducing power from NADPH to Fd in the direction opposite to that which occurs in photosynthesis. The rate of G6PDH-dependent NO2- reduction observed in vitro is capable of accounting for the observed rates of dark NO3- assimilation by C. reinhardtii.
 ...
PMID:In vitro reconstitution of electron transport from glucose-6-phosphate and NADPH to nitrite 957

Plastids from roots of barley (Hordeum vulgare L.) seedlings were isolated by discontinuous Percoll-gradient centrifugation. Coinciding with the peak of nitrite reductase (NiR; EC 1.7.7.1, a marker enzyme for plastids) in the gradients was a peak of a glucose-6-phosphate (Glc6P) and NADP(+)-linked nitrite-reductase system. High activities of phosphohexose isomerase (EC 5.3.1.9) and phosphoglucomutase (EC 2.7.5.1) as well as glucose-6-phosphate dehydrogenase (Glc6PDH; EC 1.1.1.49) and 6-phosphogluconate dehydrogenase (6PGDH; EC 1.1.1.44) were also present in the isolated plastids. Thus, the plastids contained an overall electron-transport system from NADPH coupled with Glc6PDH and 6PGDH to nitrite, from which ammonium is formed stoichiometrically. However, NADPH alone did not serve as an electron donor for nitrite reduction, although NADPH with Glc6P added was effective. Benzyl and methyl viologens were enzymatically reduced by plastid extract in the presence of Glc6P+ NADP(+). When the plastids were incubated with dithionite, nitrite reduction took place, and ammonium was formed stoichiometrically. The results indicate that both an electron carrier and a diaphorase having ferredoxin-NADP(+) reductase activity are involved in the electron-transport system of root plastids from NADPH, coupled with Glc6PDH and 6PGDH, to nitrite.
...
PMID:Nitrite reduction in barley-root plastids: Dependence on NADPH coupled with glucose-6-phosphate and 6-phosphogluconate dehydrogenases, and possible involvement of an electron carrier and a diaphorase. 2424 Sep 61

The effect of nitrate incubation on the pattern of carbohydrate metabolism in different regions of the pea (Pisum sativum L. var. Kelvedon Wonder) root has been studied. Roots were incubated in a 10 mM potassium nitrate solution for 4, 8 and 12 h. Marked increases were noted in the activities of nitrate assimilation enzymes after 4 h. Increased activities were also recorded for hexokinase, pyruvate kinase, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and transketolase. No consistent changes were observed in the activities of phosphofructokinase and glyceraldehyde-3-phosphate dehydrogenase. Experiments with [1-(14)C] and [6-(14)C]glucose indicated a relative shift in the pattern of carbohydrate oxidation from glycolysis to the pentose phosphate pathway. The data are interpreted as indicating a close interrelationship between nitrate assimilation and carbohydrate metabolism, particularly in relation to the supply of NADPH by the pentose phosphate pathway for nitrite reductase.
...
PMID:Interrelationship between nitrate assimilation and carbohydrate metabolism in plant roots. 2444 67

Enzymes representative of, and related to, the pentose phosphate pathway, glycolysis, and the tricarboxylic acid cycle have been demonstrated in supernatant and lamellar fractions of Anabaena cylindrica cultured in the presence of atmospheric nitrogen, ammonia, nitrite, and nitrate. Nitrogen-fixing and ammonia-assimilating algae contained essentially similar levels of most enzymes tested, with the notable exception of glyceraldehyde-3-phosphate dehydrogenase which showed increased NADPH-linked activity with concomitant diminution of NADH-linked activity when ammonia was supplied. The provision of nitrite or nitrate caused significant enhancements of glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, and the related hexokinase and phosphohexoisomerase. Reduced activities of pyruvate kinase, malate dehydrogenase, phosphoenolpyruvate carboxylase, and both NADH and NADPH oxidoreductases were recorded for nitrate-grown alga.The stimulation of the pentose phosphate pathway, at the partial expense of glycolysis and the tricarboxylic acid cycle, in algae cultured with nitrite and nitrate was interpreted to be due to additional NADPH requirements imposed by induced nitrite reductase. Modification of the pyridine nucleotide linkage of glyceraldehyde-3-phosphate dehydrogenase and the oxidoreductases was attributed to diversion of reductant to nitrite and nitrate reductases and nitrogenase. The results are considered to indicate regulation of blue-green algal metabolism determined by the availability of pyridine nucleotides.
...
PMID:The influence of inorganic nitrogen supply on carbohydrate and related metabolism in the blue-green alga, Anabaena cylindrica Lemm. 2445 90