Collect. Czech. Chem. Commun. 1989, 54, 819-833

Biosynthesis of water-soluble metabolites of UDP-D-galactose containing D-galactose by an enzymic preparation isolated from tissue culture of poplar (Populus alba L., var. pyramidalis)

Ladislav Bilisics and Marta Kubačková

Institute of Chemistry, Centre for Chemical Research, Slovak Academy of Sciences, 842 38 Bratislava


Biosynthesis of constituents of pectic polysaccharides containing D-galactose was investigated in poplar tissue culture in vitro. The particulate enzymic preparation isolated from the tissue culture of poplar catalyzed the transfer of D-[U-14C]-galactose unit form UDP-D-[U-14C]-galactose into various endogenous acceptors to form galactolipides, water-soluble metabolites and membrane-bound galactoproteins. The initial rate of formation of water-soluble metabolites depends on the substrate concentration and is time and amount of the enzymic protein directly proportional. Optimal formation of these metabolites proceeds at pH 7·6 and 40 °C in the presence of 0.1 mM ATP and 10 mM MgCl2. Long-term incubations afforded a mixture of three radioactive water-soluble metabolites: a neutral oligomer of Mr ~ 620 consisting at least of two β-D-[U-14C]-galactose units linked by (1 → 6) bonds and two oligomers of Mr ~ 1 400 and ≥ 2 950, respectively, containing (1 → 6) and (1 → 4)-linked D-[U-14C]-galactose units. Their relative proportion in the mixture changed in relation to incubation time and the substrate concentration. Structural features of these metabolites resembled those of D-galactans or L-rhamnogalacturonan side chains previously found in primary cell walls of some higher plants.