Document Detail

Evidence for the involvement of cell wall peroxidase in the generation of hydroxyl radicals mediating extension growth.
MedLine Citation:
PMID:  12739149     Owner:  NLM     Status:  MEDLINE    
Hydroxyl radicals (*OH), produced in the cell wall, are capable of cleaving wall polymers and can thus mediate cell wall loosening and extension growth. It has recently been proposed that the biochemical mechanism responsible for *OH generation in the cell walls of growing plant organs represents an enzymatic reaction catalyzed by apoplastic peroxidase (POD). This hypothesis was investigated by supplying cell walls of maize ( Zea mays L.) coleoptiles and sunflower ( Helianthus annuus L.) hypocotyls with external NADH, an artificial substrate known to cause *OH generation by POD in vitro. The effects of NADH on wall loosening, growth, and *OH production in vivo were determined. NADH mediates cell wall extension in vitro and in vivo in an H2O2-dependent reaction that shows the characteristic features of POD. NADH-mediated production of *OH in vivo was demonstrated in maize coleoptiles using electron paramagnetic resonance spectroscopy in combination with a specific spin-trapping reaction. Kinetic properties and inhibitor/activator sensitivities of the *OH-producing reaction in the cell walls of coleoptiles resembled the properties of horseradish POD. Apoplastic consumption of external NADH by living coleoptiles can be traced back to the superimposed action of two enzymatic reactions, a KCN-sensitive reaction mediated by POD operating in the *OH-forming mode, and a KCN-insensitive reaction with the kinetic properties of a superoxide-producing plasma-membrane NADH oxidase the activity of which can be promoted by auxin. Under natural conditions, i.e. in the absence of external NADH, this enzyme may provide superoxide (O2*-) (and H2O2 utilized by POD for) *OH production in the cell wall.
Anja Liszkay; Barbara Kenk; Peter Schopfer
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Publication Detail:
Type:  Journal Article     Date:  2003-05-09
Journal Detail:
Title:  Planta     Volume:  217     ISSN:  0032-0935     ISO Abbreviation:  Planta     Publication Date:  2003 Aug 
Date Detail:
Created Date:  2003-08-07     Completed Date:  2004-01-12     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  1250576     Medline TA:  Planta     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  658-67     Citation Subset:  IM; S    
Institut für Biologie II der Universität, Schänzlestrasse 1, 79104 Freiburg, Germany.
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MeSH Terms
Cell Wall / enzymology,  physiology
Cotyledon / drug effects,  enzymology,  physiology
Dose-Response Relationship, Drug
Helianthus / drug effects,  enzymology*,  growth & development
Hydrogen Peroxide / pharmacology
Hydroxyl Radical / metabolism*
Hypocotyl / drug effects,  enzymology,  physiology
Multienzyme Complexes / metabolism
NAD / pharmacology*
NADH, NADPH Oxidoreductases / metabolism
Peroxidase / metabolism*
Superoxides / metabolism
Zea mays / drug effects,  enzymology*,  growth & development
Reg. No./Substance:
0/Multienzyme Complexes; 11062-77-4/Superoxides; 3352-57-6/Hydroxyl Radical; 53-84-9/NAD; 7722-84-1/Hydrogen Peroxide; EC; EC 1.6.-/NADH oxidase; EC 1.6.-/NADH, NADPH Oxidoreductases

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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