The review briefly summarizes current knowledge of the bacterial nitric-oxide reductase (NOR). This membrane enzyme consists of two subunits, the smaller one contains haem C and the larger one two haems B and nonhaem iron. The protein sequence and structure of metal centres demonstrate the relationship of NOR to the family of terminal oxidases. The binuclear Fe-Fe reaction centre, consisting of antiferromagnetically coupled haem B and nonhaem iron, is analogous to Fe-Cu centre of terminal oxidases. The data on the structure and function of NOR and terminal oxidases suggest that all these enzymes are closely evolutionally related. The catalytic properties are determined most of all by the relatively high toxicity of nitric oxide as a substrate and the resulting strong need to maintain its concentration at nanomolar levels. A kinetic model of the action of the enzyme comprises substrate inhibition. NOR does not conserve the free energy of nitric oxide reduction because it does not work as a proton pump and, moreover, the protons coming into the reaction are taken from periplasm, i.e. they do not cross the membrane.

• MeSH
• Bacteria enzymologie   MeSH
• oxid dusnatý metabolismus   MeSH
• oxidoreduktasy chemie   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• nitric-oxide reductase MeSH Prohlížeč
• oxid dusnatý MeSH
• oxidoreduktasy MeSH

The metabolism of nitric oxide in Paracoccus denitrificans has been studied using a Clark-type electrode. The uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP) and the SH reagent N-ethylmaleimide, both of which released nitric oxide from cells respiring nitrite, were found to be efficient inhibitors of nitric oxide reductase activity. Control experiments with another uncoupler, pentachlorophenol, showed that the inhibitory effect of CCCP was not the result of a decrease in membrane potential. The denitrification pathway in cells with partly inhibited nitric oxide reductase, or in a reconstituted system containing purified nitric reductase and membrane vesicles, exhibited marked sustained oscillations of nitric oxide concentration. The occurrence of the oscillations was strictly dependent on the initial concentration of nitrite. The observed oscillatory kinetics is considered to reflect two regulatory signals destabilizing the denitrification pathway, namely the inhibition of nitric oxide reductase by nitric oxide and/or by nitrite.

• MeSH
• biologický transport MeSH
• buněčná membrána účinky léků   fyziologie   MeSH
• cytochromy skupiny c metabolismus   MeSH
• ethylmaleimid farmakologie   MeSH
• karbonylkyanid-m-chlorfenylhydrazon farmakologie   MeSH
• kinetika MeSH
• membránové potenciály účinky léků   MeSH
• nitritreduktasy izolace a purifikace   metabolismus   MeSH
• oxid dusnatý metabolismus   MeSH
• oxidoreduktasy izolace a purifikace   metabolismus   MeSH
• Paracoccus denitrificans metabolismus   fyziologie   MeSH
• pentachlorfenol farmakologie   MeSH
• rozpřahující látky farmakologie   MeSH
• spotřeba kyslíku účinky léků   MeSH
• transport elektronů účinky léků   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• cytochromy skupiny c MeSH
• ethylmaleimid MeSH
• karbonylkyanid-m-chlorfenylhydrazon MeSH
• nitric-oxide reductase MeSH Prohlížeč
• nitritreduktasy MeSH
• oxid dusnatý MeSH
• oxidoreduktasy MeSH
• pentachlorfenol MeSH
• rozpřahující látky MeSH