Abstract
The substrate specificity of two recombinant enzymes, zeatin O-glucosyltransferase 1 (ZOG1) and zeatin O-xylosyltransferase 1 (ZOX1), was further characterised. ZOG1 utilises zeatin (Z), UDPG, and UDPX as substrates to form O-glucosylzeatin (OGZ) and O-xylosylzeatin (OXZ) but has higher affinity to UDPG than UDPX. ZOX1 uses only UDPX, converting Z to OXZ. Dihydrozeatin (DHZ) is also a substrate for both enzymes, but only in combination with UDPX, giving rise to O-xylosyldihydrozeatin (OXDHZ). O-Glucosyldihydrozeatin (OGDHZ) is not formed by ZOG1, possibly due to steric hindrance. Regions relevant to UDPG/UDPX affinity and competition were identified using hybrid enzymes derived from domain exchanges of parental genes. The N-terminal half of the enzyme is important in this respect. The BstEII-BstAPI segment of ZOG1 correlates with inhibition of O-xylosyltransferase activity by UDPG while the BstAPI-Eco0109 segment of ZOG1 is required for utilisation of UDPG as the sugar donor.
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Martin, R., Cloud, K., Mok, M. et al. Substrate specificity and domain analyses of zeatin O-glycosyltransferases. Plant Growth Regulation 32, 289–293 (2000). https://doi.org/10.1023/A:1010708001981
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DOI: https://doi.org/10.1023/A:1010708001981