Evidence for Involvement of the Superoxide Radical in the Conversion of 1-Aminocyclopropane-1-Carboxylic Acid to Ethylene by Pea Microsomal Membranes |
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| Authors: | McRae D G; Baker J E; Thompson J E |
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| Institution: | 1Department of Biology, University of Waterloo Waterloo, Ontario, Canada N2L 3G1
2Plant Hormone Laboratory, ARS, Plant Physiology Institute USDA, Beltsville, MD. 20705, U.S.A. |
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| Abstract: | Electron spin resonance (ESR) spectroscopy has provided evidencefor involvement of the superoxide anion (O2–) radicalin the conversion of l-aminocyclopropane-l carboxylic acid (ACC)to ethylene by microsomal membranes from etiolated pea seedlings.Formation of ethylene from ACC by the membrane system is oxygen-dependent,heat denaturable, inhibited by the radical scavenger n-propylgallate and sensitive to superoxide dismutase (SOD) and catalase.Addition of 1,2-dihydroxybenzene-3,5-disulfonic acid (Tiron)to the reaction mixture results in formation of the Tiron semiquinone(Tiron radical) ESR signal derived from O2–, and alsoinhibits ethylene production. The radical signal is oxygen-dependentand inhibited by SOD and catalase, but is formed both in thepresence and absence of ACC. Heat denaturation of the microsomalenzyme system completely blocks formation of the radical signal.The data collectively suggest that O2– generated by amembrane-bound enzyme facilitates the conversion of ACC to ethylene. (Received September 8, 1981; Accepted January 19, 1982) |
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