The roles of calcium and manganese ions in the in vitro conversion of 1-aminocyclopropane-1-carboxylic acid to ethylene by lentil root membranes |
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Authors: | Claude Penel Thomas Gaspar Michèle Crèvecoeur Claire Kevers Hubert Greppin |
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Institution: | Lab, of Plant Physiology, 3, place de l'Université, C H-1211 Genève 4, Switzerland;Inst. of Botany B 22, Univ. of Liège –Sart Tilman, B-4000 Liège, Belgium |
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Abstract: | Ca2+ and Mn2+ activate the conversion of 1-aminocyclopropane-1-carboxylic acid (ACC) by root microsomes of Vicia lens as they do in other similar systems. The preparation of microsomes in the presence of Mn2+ greatly increases their ability to convert ACC into ethylene, without addition of Mn2+ in the reaction mixture. Ca2+ does not have this property. The effect could not be attributed to Mn2+ entrapping into membrane vesicles (sonication followed by repelleting had no effect) but, possibly, in part to Mn2+-mediated binding to microsomes of a soluble factor favouring the conversion of ACC to C2H4. Although no direct correlation could be established in vitro between ethylene-forming-enzyme (EFE) and peroxidase activities, some soluble peroxidases might be this soluble factor. Mn2+ favoured attachment to membranes of some peroxidase activity from the soluble fraction and from commercial HRP and lipoxygenase. This binding effect of Mn2+ cannot be readily distinguished from its role in the generation of a chain of free radicals and in redox mechanisms. |
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Keywords: | Calcium ethylene-forming enzyme lentil manganese membranes peroxidase Vicia lens |
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