Possible mechanism of nitric oxide production from N(G)-hydroxy-L-arginine or hydroxylamine by superoxide ion

It has been speculated the N(G)-hydroxy-L-arginine (OH-L-Arg), which is an intermediate in NO production from L-arginine, may be converted to NO by superoxide ion. However, there is still no direct evidence for this conversion. In the present study this was investigated using superoxide ion generate...

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Bibliographic Details
Published in:The international journal of biochemistry & cell biology 1996-12, Vol.28 (12), p.1311-1318
Main Authors: Vetrovsky, P, Stoclet, J C, Entlicher, G
Format: Article
Language:English
Subjects:
Animals
Arginine - analogs & derivatives
Arginine - metabolism
Cell Line
Hydrogen-Ion Concentration
Hydroxylamine
Hydroxylamines - metabolism
In Vitro Techniques
Macrophage Activation
Male
Mice
Microsomes, Liver - metabolism
Nitrates - metabolism
Nitric Oxide - biosynthesis
Nitrites - metabolism
Oxidation-Reduction
Rats
Rats, Wistar
Solutions
Superoxides - metabolism
Water
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Summary:It has been speculated the N(G)-hydroxy-L-arginine (OH-L-Arg), which is an intermediate in NO production from L-arginine, may be converted to NO by superoxide ion. However, there is still no direct evidence for this conversion. In the present study this was investigated using superoxide ion generated either in acellular or cellular systems. It was found that OH-L-Arg and hydroxylamine were converted to nitrite and nitrate apparently via NO by superoxide ion in aqueous solution. Arginine remained unaffected. These changes were observed during reaction of chemical substances as well as in a biological system (zymosan-activated macrophages in culture). Superoxide dismutase prevented this transformation. OH-L-Arg was also spontaneously hydrolysed to hydroxylamine and L-citrulline, however this occurred at pH > 9 only. Activated microsomes (containing different isoforms of cytochrome P450) were unable to replace NO-synthase in its ability to produce OH-L-Arg from L-arginine. These data support the hypothesis that a pathway alterative to the well-known synthesis of NO by NO-synthase via OH-L-Arg exists. This pathway may involve the production of OH-L-Arg by NO-synthase and decomposition of OH-L-Arg to NO by the action of superoxide ion. Alternatively, hydrolysis of OH-L-Arg to hydroxylamine may occur followed by its oxidation to NO, again by superoxide ion.
ISSN:1357-2725
DOI:10.1016/S1357-2725(96)00089-1