Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Pivot Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Target Concepts:
Gene/Protein
Disease
Symptom
Drug
Enzyme
Compound
Query: EC:1.7.1.2 (
nitrate reductase
)
3,861
document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)
A spontaneous mutant of Rhodobacter sphaeroides f. sp. denitrificans IL-106 was found to excrete a large amount of a red compound identified as coproporphyrin III, an intermediate in bacteriochlorophyll and heme synthesis. The mutant, named PORF, is able to grow under phototrophic conditions but has low levels of intracellular cysteine and glutathione and overexpresses the
cysteine synthase
CysK. The expression of molybdoenzymes such as dimethyl sulfoxide (DMSO) and nitrate reductases is also affected under certain growth conditions. Excretion of coproporphyrin and overexpression of CysK are not directly related but were both found to be consequences of a diminished synthesis of the key metabolite S-adenosylmethionine (SAM). The wild-type phenotype is restored when the gene metK encoding SAM synthetase is supplied in trans. The metK gene in the mutant strain has a mutation leading to a single amino acid change (H145Y) in the encoded protein. This point mutation is responsible for a 70% decrease in intracellular SAM content which probably affects the activities of numerous SAM-dependent enzymes such as coproporphyrinogen oxidase (HemN); uroporphyrinogen III methyltransferase (CobA), which is involved in siroheme synthesis; and molybdenum cofactor biosynthesis protein A (MoaA). We propose a model showing that the attenuation of the activities of SAM-dependent enzymes in the mutant could be responsible for the coproporphyrin excretion, the low cysteine and glutathione contents, and the decrease in DMSO and
nitrate reductase
activities.
...
PMID:Coproporphyrin excretion and low thiol levels caused by point mutation in the Rhodobacter sphaeroides S-adenosylmethionine synthetase gene. 2003 86
Salinity is one of the abiotic factors that most affect crop growth and production. This study focused on the effect of high salinity on the endogenous levels of the signaling molecules hydrogen sulfite (H
2
S) and nitric oxide (NO) in Nicotiana tabacum leaves and the extent of these for the biochemically-driven plant tolerance to such abiotic stress. The NaCl treatment for 10days led to an expressive augment of H
2
S and NO levels. This increase was correlated with the raise of l-Cys and l-Arg and the induction of l-cysteine desulfhydrase, cyanoalanine synthase,
cysteine synthase
,
nitrate reductase
and arginase, enzymes known to be involved in the biosynthesis of H
2
S or NO. The enzymatic antioxidant system (superoxide dismutase and catalase activity) was boosted and the non-enzymatic antioxidant glutathione was intensively oxidized in leaves upon stress allowing plants to cope with oxidative stress. Lower stomatal conductance was observed in stressed plants in comparison with control ones. Moreover, the high activity of antioxidant enzymes and high rate of glutathione oxidation following salt stress were considerably decreased upon NO or H
2
S scavenging. Thus, increment in NO and H
2
S levels and their interplay, along with metabolic and physiological changes, contributed to tobacco survival to extreme salinity conditions.
...
PMID:Salinity-induced accumulation of endogenous H
2
S and NO is associated with modulation of the antioxidant and redox defense systems in Nicotiana tabacum L. cv. Havana. 2816 28
