Cytokinin oxidase from Phaseolus vulgaris callus tissues. Enhanced in vitro activity of the enzyme in the presence of copper-imidazole complexes
The effects of metal ions on cytokinin oxidase activity extracted from callus tissues of Phaseolus vulgaris L. cv Great Northern have been examined using an assay based on the oxidation of N/sup 6/-(..delta../sup 2/-isopentenyl)-adenine-2,8-/sup 3/H (i/sup 6/ Ade) to adenine (Ade). The addition of cupric ions to reaction mixtures containing imidazole buffer markedly enhanced cytokinin oxidase activity. In the presence of optimal concentrations of copper and imidazole, cytokinin oxidase activity was stimulated more than 20-fold. The effect was enzyme dependent, specific for copper, and observed only in the presence of imidazole. The substrate specificity of the copper-imidazole enhanced reaction, as judged by substrate competition tests, was the same as that observed in the absence of copper and imidazole. Similarly, in tests involving DEAE-cellulose chromatography, elution profiles of cytokinin oxidase activity determined using a copper-imidazole enhanced assay were identical to those obtained using an assay without copper and imidazole. On the basis of these results, the addition of copper and imidazole to reaction mixtures used to assay for cytokinin oxidase activity is judged to provide a reliable and specific assay of greatly enhanced sensitivity for the enzyme. The mechanism by which copper and imidazole enhance cytokinin oxidase activity is not certain, but the reaction catalyzed by the enzyme was not inhibited by anaerobic conditions when these reagents were present. This observation suggests that copper-imidazole complexes are substituting for oxygen in the reaction mechanism by which cytokinin oxidase effects cleavage of the N/sup 6/-side chain of i/sup 6/ Ade.
- Research Organization:
- Oregon State Univ., Corvallis, OR (United States)
- OSTI ID:
- 6061591
- Journal Information:
- Plant Physiol.; (United States), Vol. 84:3
- Country of Publication:
- United States
- Language:
- English
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59 BASIC BIOLOGICAL SCIENCES
COPPER
BIOLOGICAL EFFECTS
OXIDOREDUCTASES
QUANTITATIVE CHEMICAL ANALYSIS
ADENINES
ANAEROBIC CONDITIONS
BUFFERS
CATIONS
ENZYME ACTIVITY
IMIDAZOLES
ION EXCHANGE CHROMATOGRAPHY
OXIDATION
OXYGEN
PHASEOLUS
PLANT GROWTH REGULATORS
PLANT TISSUES
STIMULATION
TRACER TECHNIQUES
TRITIUM COMPOUNDS
AMINES
ANTIMETABOLITES
AROMATICS
AZAARENES
AZOLES
BACTERIA
BODY
CHARGED PARTICLES
CHEMICAL ANALYSIS
CHEMICAL REACTIONS
CHROMATOGRAPHY
DRUGS
ELEMENTS
ENZYMES
HETEROCYCLIC COMPOUNDS
IONS
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
LEGUMINOSAE
METALS
MICROORGANISMS
NONMETALS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PLANTS
PURINES
RHIZOBIUM
SEPARATION PROCESSES
TISSUES
TRANSITION ELEMENTS
560300* - Chemicals Metabolism & Toxicology
551001 - Physiological Systems- Tracer Techniques