Salicylic acid is a modulator of tobacco and mammalian catalases.
Salicylic acid (SA) plays a key role in the establishment of resistance to microbial pathogens in many plants. The discovery that SA inhibits catalase from tobacco led us to suggest that H2O2 acts as second messenger to activate plant defenses. Detailed analyses of SA's interaction with tobacco and mammalian catalases indicate that SA acts as an electron donor for the peroxidative cycle of catalase. When H2O2 fluxes were relatively low (1 microM/min or less), SA inhibited catalase, consistent with its suggested signaling function via H2O2. However, significant inhibition was only observed at 100 microM SA or more, a level reached in infected, but not in uninfected, leaves. This inhibition was probably due to siphoning catalase into the slow peroxidative reaction. Surprisingly, SA was also able to protect catalase from inactivation by damaging levels of H2O2 (lower millimolar range), which is generally assumed to reflect accumulation of inactive ferro-oxy intermediates. SA did so by supporting or substituting for the protective function of catalase-bound NADPH. These results add new features to SA's interaction with heme enzymes and its in vivo redox properties. Thus, SA, in addition to its proposed signaling function, may also have an important antioxidant role in containing oxidative processes associated with plant defense responses.
Waksman Institute and Department of Molecular Biology and Biochemistry, Rutgers, The State University of New Jersey, P. O. Box 759, Piscataway, New Jersey 08855, USA.
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Durner
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Klessig
D000818:Animals; D002374:Catalase / Q000378:metabolism*; D002417:Cattle; D004791:Enzyme Inhibitors / Q000378:metabolism*; D016166:Free Radical Scavengers / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D007527:Isoenzymes / Q000302:isolation & purification / Q000378:metabolism; D008956:Models, Chemical; D009249:NADP / Q000378:metabolism; D030821:Plants, Genetically Modified; D010947:Plants, Toxic; D012459:Salicylates / Q000378:metabolism*; D020156:Salicylic Acid; D014026:Nicotiana
D004791:Enzyme Inhibitors; D016166:Free Radical Scavengers; D007527:Isoenzymes; D012459:Salicylates; D009249:NADP; D002374:Catalase; D020156:Salicylic Acid