Flavoprotein and peroxidase as components of the indoleacetic acid oxidase system of peas |
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| Authors: | GALSTON A W BONNER J BAKER R S |
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| Affiliation: | 1. School of Agriculture and Food Sciences, The University of Queensland, St Lucia, QLD 4072, Australia;2. Science and Technology Division, Department of Environment and Science, GPO Box 2454, Brisbane, QLD 4001, Australia;3. Soil Science Division, Bangladesh Institute of Nuclear Agriculture, Mymensingh 2202, Bangladesh;4. Australian Institute of Bioengineering and Nanotechnology, St Lucia, QLD 4072, Australia |
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| Abstract: | - 1.1. Several lines of evidence indicate that the IAA-oxidase system of peas consists of a light-activatable flavoprotein enzyme coupled through H2O2 to a peroxidase.
- 1.1.(a) The system is inhibited by catalase, the inhibition being reversed by blue light.
- 1.2.(b) The activity of the system is increased by the addition of H2O2 in the dark, and by the addition of crystalline horseradish root peroxidase in the light. This indicates that H2O2 limits the reaction in the dark; in the light, H2O2 production is increased and the peroxidase becomes limiting.
- 1.3.(c) Crystalline horseradish root peroxidase readily oxidizes IAA in the presence of H2O2.
- 1.4.(d) The IAA-oxidase system has been separated into a peroxidase and a flavin-containing component. The peroxidase component is active in the presence of H2O2 in oxidizing IAA and conventional peroxidase substrates. Successful reconstitution of the IAA-oxidase system from its fragments has been achieved. The substrate for the flavin enzyme is unknown, but may be IAA itself.
- 1.5.(e) An analog of the IAA-oxidase system has been made by combining the xanthine oxidase of cream with the crystalline peroxidase of horseradish root. The analog system differs from IAA oxidase in requiring a substrate other than IAA for the flavoprotein.
- 2.2. Possible alternative schemes have been examined.
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