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
- OSTI ID:
- 6061591
- Journal Information:
- Plant Physiol.; (United States), Journal Name: Plant Physiol.; (United States) Vol. 84:3; ISSN PLPHA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
560300* -- Chemicals Metabolism & Toxicology
59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ADENINES
AMINES
ANAEROBIC CONDITIONS
ANTIMETABOLITES
AROMATICS
AZAARENES
AZOLES
BACTERIA
BIOLOGICAL EFFECTS
BODY
BUFFERS
CATIONS
CHARGED PARTICLES
CHEMICAL ANALYSIS
CHEMICAL REACTIONS
CHROMATOGRAPHY
COPPER
DRUGS
ELEMENTS
ENZYME ACTIVITY
ENZYMES
HETEROCYCLIC COMPOUNDS
IMIDAZOLES
ION EXCHANGE CHROMATOGRAPHY
IONS
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
LEGUMINOSAE
METALS
MICROORGANISMS
NONMETALS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXIDATION
OXIDOREDUCTASES
OXYGEN
PHASEOLUS
PLANT GROWTH REGULATORS
PLANT TISSUES
PLANTS
PURINES
QUANTITATIVE CHEMICAL ANALYSIS
RHIZOBIUM
SEPARATION PROCESSES
STIMULATION
TISSUES
TRACER TECHNIQUES
TRANSITION ELEMENTS
TRITIUM COMPOUNDS