Title: Biochemical characterization of 1-aminocyclopropane-1-carboxylate oxidase in mung bean hypocotyls
Abstract: The final step in ethylene biosynthesis is catalyzed by the enzyme 1-aminocyclopropane-l-carboxylate (ACC) oxidase. ACC oxidase was extracted from mung bean hypocotyls and its biochemical characteristics were determined. In vitro ACC oxidase activity required ascorbate and Fe^(2+), and was enhanced by sodium bicarbonate. Maximum specific activity (approximately 20 nl ethylene h^(-1) mg protein^(-1)) was obtained in an assay medium containing 100 mM MOPS (pH 7.5), 25 μM FeSO₄, 6 mM sodium ascorbate, 1 mM ACC, 5 mM sodium bicarbonate and 10% glycerol. The apparent K_m for ACC was 80±3μM. Pretreating mung bean hypocotyls with ethylene increased in vitro ACC oxidase activity twofold. ACC oxidase activity was strongly inhibited by metal ions such as Co^(2+), Cu^(2+), Zn^(2+), and Mn^(2+), and by salicylic acid. Inactivation of ACC oxidase by salicylic acid could be overcome by increasing the Fe^(2+) concentration of the assay medium. The possible mode of inhibition of ACC oxidase activity by salicylic acid is discussed.
Publication Year: 1998
Publication Date: 1998-01-31
Language: en
Type: article
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