Table 1.
Relative affinity of recombinant protein to cytokinin and glycosyl substrates
| Exp. | Substrates | Product, cpm (%) | Substrate left, cpm (%) |
|---|---|---|---|
| A | Z + UDPG | OGZ | Z |
| 39,715 (100) | 0 (0) | ||
| Z + UDPX | OXZ | Z | |
| 4,956 (18) | 23,078 (82) | ||
| B | Z + UDPG | OGZ | Z |
| 3,731 (14) | 23,115 (86) | ||
| DZ + UDPG | OGDHZ | DHZ | |
| 329 (1) | 24,178 (99) |
DHZ, dihydrozeatin; OGZ, O-glucosylzeatin; OGDHZ, O-glucosyldihydrozeatin; OXZ, O-xylosylzeatin; Z, trans-zeatin; UDPG, UDPglucose; UDPX, UDPxylose. For experiment A, 200 μl of supernatant from lysed cells containing the recombinant protein was incubated with approximately 1 nmol of 14C-labeled zeatin for 2 h, and the reaction products were separated by HPLC. UDPglucose as the glycosyl donor resulted in zeatin depletion, and UDPxylose serving as the glycosyl donor resulted in much lower formation of the corresponding product, OXZ. For experiment B, DEAE-purified proteins (4 μg) were incubated with approximately 0.5 nmol of [14C]cytokinins for 2 h. Only a trace of O-glucosyldihydrozeatin was formed.