Kinetic Comparison of Cytokinin Nucleosidase Activity Isolated from Normally Ripening and Mutant Tomato Varieties

Kinetic parameters for cytokinin nucleosidase activity which catalyzes the deribosylation of N6(Δ 2-isopentenyl)adenosine ($\text{I}^{6}$Ado) to produce the more "active" free base $N^{5}$(Δ 2-isopenetyl)adenine ($\text{I}^{6}$Ade) were compared for a normally ripening tomato (Lycopersicon esculentum L.) cultivar Rutgers, and two mutant tomato varieties (Nor and Rin). Km for nucleosidase activity in Rutgers was lower (Km = 0.1 millimolar) than that in either Nor (Km = 0.14 millimolar) or Rin (Km = 0.13 millimolar).