Cytokinin oxidase fromZea mays kernels andVinca rosea crown-gall tissue

• Published in: Planta Vol. 159; no. 1; p. 30
• Main Authors: McGaw, B A, Horgan, R
• Format: Journal Article
• Language: English
• Published: Germany 01.01.1983
• ISSN: 0032-0935
• DOI: 10.1007/bf00998811

Cytokinin oxidase has been partially purified from matureZea mays kernels and fromVinca rosea corwn-gall tissue. The molecular weights of the two enzymes, determined by gel filtration, are very different: 94,400 (±10%) forZ. mays and 25,100 (±10%) forV. rosea. Specificity studies have been performed using a large number of synthetic and naturally occurring cytokinins. Only a small number of these compounds serve as substrates and both enzymes exhibit similar substrate specificity. In agreement with other workers, a Δ(2) double bond in the N(6) side chain is essential for activity. The presence of glucosyl or ribosyl groups in the 7-or 9-position or an alanyl group in the 9-position of the purine moiety have little effect on their susceptibility to cytokinin oxidase, but O-glucosyl derivatives are resistant to oxidation. The relevance of these enzyme systems to studies on cytokinin metabolism and to the endogenous cytokinins is discussed.