Eva Kavkova

Abstract

Nucleotide sugars are activated forms of monosaccharides and serve as glycosyl donors for glycosyltransferases e.g. in the synthesis of cell wall polysaccharides. Nucleotide sugars are mainly created de novo from products of photosynthesis. During plant metabolism are however free monosaccharides being released. These monosaccharides can be again activated via salvage pathways. Sugar kinases play an important role in the first step of conversion sugars into nucleotide sugars in both cases – in the synthesis as well as in the nucleotide sugars recycling.
This project is focused on sugar-1-kinases from higher plants, which are up to now not so well characterized. In the first part, an arabinokinase from A. thaliana will be investigated. This enzyme is part of the nucleotide sugars recycling (salvage) pathway. A mutant with a point mutation in the kinase domain was previously identified. This mutation is lethal for plants when grown on medium containing arabinose. We will test several hypotheses to explain the lethal phenotype. A further topic deals with xylose metabolism in plants. It is so far unclear, if the salvage pathway, containing a putative enzyme xylokinase, also exists or if this sugar is metabolized different route – via xylulose – and goes to the pentose phosphate pathway.  
Better understanding of sugar kinases and metabolism of nucleotide sugars could in future at least partially help to regulate plant biomass and cell wall composition.