XXII. BIOCHEMICKÝ ZJAZD - Jesseniova lekárska fakulta

Lectures
TraNSGLYCOSYLATION - a UNIVERSAL PRINCIPLE IN TAILORING
THE PLANT AND FUNGAL CELL WALLS
Vladimír Farkaš
Institute of Chemistry, Center for Glycomics, Slovak Academy of Sciences, Department
of Glycobiology, Dúbravská cesta 9, 84538 Bratislava, Slovakia
Plant and fungal cell walls are composite structures composed of polysaccharides and
protein-polysaccharides mutually cross-linked by non-covalent interactions and covalent
bonds. Individual wall polymers are being synthesized separately, either intracellularly
or at the plasma membrane and exported into the cell wall. The final stage of cell wall
formation involves the formation of cross-links between the individual polymer molecules,
either of the same or of the diverse types. The enzymes catalyzing the latter
type of reactions are transglycosylases. They are either GPI-anchored to the plasma
membrane or embedded in the cell wall. As an example from the plant kingdom, the
enzyme xyloglucan endotransglycosylase (XET) will be presented. The enzyme catalyzes
cleavage of xyloglucan molecules and transferring the cleaved fragments to other xyloglucan
molecules in the plant cell walls. Transglycosylases operate also in the fungal
cell walls. As the examples can serve the β-1,3-glucan elongases of the Gas family or
the chitin endotransglycosylases of the Crh family from yeast. Biochemical properties
of these enzymes heterologously expressed in Pichia were determined in vitro using
specially devised assays. In these assays, soluble polysaccharide derivatives were used as
the glycosyl donors and diverse fluorescently labeled oligosaccharides as the acceptors.
As the measure of enzyme activity served the amount of the fluorescence incorporated
into the polymer.
56 XXII. Biochemistry Congress, Martin