Nitric oxide (NO) generated from nitrite through nitrite reductase activity in red blood cells has been proposed to play a major role in hypoxic vasodilation. However, we have previously predicted from mathematical modeling that much more NO can be derived from tissue nitrite reductase activity than from red blood cell nitrite reductase activity. Evidence in the literature suggests that tissue ...

Elevation of circulating nitrite (NO2(-)) levels causes vasodilatation and lowers blood pressure in healthy volunteers. Whether these effects and the underpinning mechanisms persist in hypertension is unknown. Therefore, we investigated the consequences of systemic nitrite elevation in spontaneously hypertensive rats and conducted proof-of-principle studies in patients. Nitrite caused dose-depe...

Plant NiR (nitrite reductase) and SiR (sulfite reductase) have common structural and functional features. Both enzymes are generally distinguished in terms of substrate specificity for nitrite and sulfite. The genome of Cyanidioschyzon merolae, a unicellular red alga living in acidic hot springs, encodes two SiR homologues, namely CmSiRA and CmSiRB (C. merolae sulfite reductases A and B), but n...

The rpoN region of Pseudomonas stutzeri was cloned, and an rpoN null mutant was constructed. RpoN was not essential for denitrification in this bacterium but affected the expression levels and enzymatic activities of cytochrome cd1 nitrite reductase and nitric oxide reductase, whereas those of respiratory nitrate reductase and nitrous oxide reductase were comparable to wild-type levels. Since t...

Introduction Sulfur is required for the biosynthesis of several essential compounds like amino acids (cysteine and methionine), vitamins (biotin, thiamin), and prosthetic groups (Fe-S clusters) in all organisms. In order to synthesize these compounds, the sulfur has usually to be in a reduced state, most commonly as (hydrogen) sulfide. In the absence of an environmental supply of reduced sulfur...

Cytochrome P-450 LM2 reduction was measured at a series of NADPH concentrations in the absence of substrate and in the presence of 1 mM benzphetamine. In the absence of substrate reduction could be described as a biphasic process with 55% of the reaction occurring in the first phase (at 20 microM NADPH). When benzphetamine was present, the fraction of the reaction occurring in the first phase w...

NADPH-cytochrome c reductase was solubilized from the microsomal fraction of Petunia hybrida flowers by 3-[(3-cholamidopropyl)dimethylammonio]-1-propane sulfonate detergent and purified by adenosine 2',5'-bisphosphate-Sepharose chromatography, followed by high-performance anion-exchange chromatography. Two proteins with molecular sizes of 75 and 81 kD were detected in the purified preparation b...

A barley (Hordeum vulgare L.) mutant, nar1a (formerly Az12), deficient in NADH nitrate reductase activity is, nevertheless, capable of growth with nitrate as the sole nitrogen source. In an attempt to identify the mechanism(s) of nitrate reduction in the mutant, nitrate reductase from nar1a was characterized to determine whether the residual activity is due to a leaky mutation or to the presenc...

AtCBR, a cDNA encoding NADH-cytochrome (Cyt) b5 reductase, and AtB5-A and AtB5-B, two cDNAs encoding Cyt b5, were isolated from Arabidopsis. The primary structure deduced from the AtCBR cDNA was 40% identical to those of the NADH-Cyt b5 reductases of yeast and mammals. A recombinant AtCBR protein prepared using a baculovirus system exhibited typical spectral properties of NADH-Cyt b5 reductase ...