Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.7.1.2 (nitrate reductase)
 3,861 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This work is concerned with the metabolism of Caldithrix abyssi-an anaerobic, moderately thermophilic bacterium isolated from deep-sea hydrothermal vents of the Mid-Atlantic Ridge and representing a new, deeply deviated branch within the domain Bacteria. Cells of C. abyssi grown on acetate and nitrate, which was reduced to ammonium, possessed nitrate reductase activity and contained cytochromes of the b and c types. Utilization of acetate occurred as a result of the operation of the TCA and glyoxylate cycles. During growth of C. abyssi on yeast extract, fermentation with the formation of acetate, propionate, hydrogen, and CO2 occurred. In extracts of cells grown on yeast extract, acetate was produced from pyruvate with the involvement of the following enzymes: pyruvate:ferredoxin oxidoreductase (2.6 micromol/(min mg protein)), phosphate acetyltransferase (0.46 micromol/(min mg protein)), and acetate kinase (0.3 micromol/(min mg protein)). The activity of fumarate reductase (0.14 micromol/(min mg protein)), malate dehydrogenase (0.17 micromol/(min mg protein)), and fumarate hydratase (1.2 micromol/(min mg protein)), as well as the presence of cytochrome b, points to the formation of propionate via the methyl-malonyl-CoA pathway. The activity of antioxidant enzymes (catalase and superoxide dismutase) was detected. Thus, enzymatic mechanisms have been elucidated that allow C. abyssi to switch from fermentation to anaerobic respiration and to exist in the gradient of redox conditions characteristic of deep-sea hydrothermal vents.
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PMID:[Investigation of the catabolism of acetate and peptides in the new anaerobic thermophilic bacterium Caldithrix abyssi]. 1675 61

Synthesis of the Escherichia coli YtfE protein, also known as RIC, for the repair of damaged iron centres, is highly induced during anaerobic growth under conditions of nitrosative stress. How YtfE repairs nitrosative damage remains unclear. Contrary to previous reports, we show that strains defective in YtfE that lack the high-affinity NO reductase activity of the hybrid cluster protein (Hcp) are less sensitive to nitrosative stress than isogenic ytfE+ strains, which are extremely sensitive. Evidence that this sensitivity is due to YtfE-dependent release of NO into the cytoplasm includes: relief of growth inhibition by PTIO (2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide), which degrades NO; relief of nitrosative stress by deletion of narG encoding the nitrate reductase that is the major source of NO from nitrite; partial suppression of nitrosative stress due to loss of Hcp function by a further mutation in ytfE; YtfE-dependent loss of aconitase and fumarase activities in the absence of Hcp; and YtfE-dependent relief of NsrR repression of the hcp promoter in response to cytoplasmic NO. We suggest that a major role for YtfE is to reverse nitrosative damage by releasing, directly or indirectly, NO from nitrosylated proteins into the cytoplasm where the high-affinity NO reductase activity of Hcp ensures its reduction to N2O. If so, the concerted action of YtfE and Hcp would not only maintain the cytoplasmic concentration of NO in the low nM range, but also provide a rationalization for the coordinate regulation of Hcp and YtfE synthesis by NsrR.
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PMID:Release of nitric oxide by the Escherichia coli YtfE (RIC) protein and its reduction by the hybrid cluster protein in an integrated pathway to minimize cytoplasmic nitrosative stress. 2949 96