Plant Physiology 90:899-906 (1989)
© 1989 American Society of Plant Biologists
Metabolism and Enzymology
Cytokinin Oxidase from Wheat
Partial Purification and General Properties
Michel Laloue1 and
J. Eugene Fox2
ARCO Plant Cell Research Institute, Dublin, California 94568
As part of the study of the possible role(s) of CBF-1, a cytokinin-binding protein abundant in wheat embryo, a cytokinin oxidase was found in wheat (Triticum aestivum L.) germ and partially purified by conventional purification techniques and high performance chromatofocusing. This preparation catalyzes conversion of N6-( 2-isopentenyl)adenosine to adenosine at a Vmax of 0.4 nanomol per milligram protein per minute at 30°C and pH 7.5, the Km being 0.3 micromolar. This high affinity and the apparent molecular weight of 40,000 estimated by high performance gel permeation on a Spherogel TSK-3000 SW column indicate that this enzyme is different from other cytokinin oxidases previously reported. Oxygen is required for the reaction, as for other cytokinin oxidases already described. N6-(2-isopentenyl)adenine and zeatin riboside are also degraded, but N6-(2-isopentenyl)adenosine-5'-monophosphate is apparently not a substrate. Benzyladenine is degraded, but to a small extent, and it inhibits slightly the degradation of N6-(2-isopentenyl)adenosine. The degradation of N6-(2-isopentenyl)adenosine is strongly inhibited by diphenylurea and its highly active derivative N-(2-chloro-4-pyridyl)-N'-phenylurea.
1 Present address, Laboratoire de Physiologie Cellulaire Végétale, CNRS, 91198 Gif-sur-Yvette Cedex, France.
2 Present address, Miles Laboratories, Inc, P. O. Box 932, Elkhart, IN 46515.
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