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Plant Physiology 61:107-110 (1978) © 1978 American Society of Plant Biologists Cucumber Seedling Indoleacetaldehyde Oxidase 1Biochemistry and Biophysics Section, Biological Sciences Group, University of Connecticut, Storrs, Connecticut 06268
Extracts of light-grown Cucumis sativus L. seedlings catalyzed the oxidation of indole-3-acetaldehyde to indole-3-acetic acid. No added cofactors were required. Inhibitor studies indicated that the enzyme is a metalloflavoprotein. While indole-3-aldehyde, benzaldehyde, and phenylacetaldehyde partially inhibited the oxidation of indole-3-acetaldehyde, suggesting that they may serve as alternative substrates, it is proposed that indoleacetaldehyde is the major substrate in vivo. 2,4-Dichlorophenoxyacetic acid strongly inhibited the indoleacetaldehyde oxidase activity, and it is proposed that this enzyme may be subject in vivo to feedback inhibition by indole-3-acetic acid. The enzyme was activated by brief heating or by treatment with mercaptoethanol.
2 University Scholar, Undergraduate Honors Program, University of Connecticut. 3 Present address: Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403. 4 Present address: Biology Department, Harvey Mudd College, Claremont, California 91711. 1 This work was supported by the University of Connecticut Research Foundation and by National Science Foundation Grant GB-40556 to W. K. P.
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