ABSTRACT
The presence of various enzyme forms with terminal action pattern on pectate was evaluated in a protein mixture obtained from parsley roots. Enzymes found in the soluble fraction of roots (juice) were purified to homogeneity according to SDS-PAGE, partially separated by preparative isoelectric focusing and characterized. Three forms with pH optima 3.6, 4.2 and 4.6 clearly preferred substrates with a lower degree of polymerization (oligogalacturonates) while the form with pH optimum 5.2 was a typical exopolygalacturonase [EC 3. 2.1.67] with relatively fast cleavage of polymeric substrate. The forms with pH optima 3.6, 4.2 and 5.2 were released from the pulp, too. The form from the pulp with pH optimum 4.6 preferred higher oligogalacturonates and was not described in plants previously. The production of individual forms in roots was compared with that produced by root cells cultivated on solid medium and in liquid one.
Subject(s)
Petroselinum/enzymology , Polysaccharide-Lyases/metabolism , Animals , Electrophoresis, Polyacrylamide Gel , Glycoside Hydrolases/metabolism , Hydrogen-Ion Concentration , Isoelectric Focusing , Kinetics , Mice , Mixed Function Oxygenases/isolation & purification , Mixed Function Oxygenases/metabolism , Plant Roots/enzymology , Polysaccharide-Lyases/isolation & purificationABSTRACT
Using combinations of different polysaccharides as glycosyl donors and of oligosaccharides fluorescently labeled by sulforhodamine (SR) as glycosyl acceptors, we screened for the presence of transglycosylating activities in extracts from nasturtium (Tropaeolum majus). Besides xyloglucan endotransglycosylase/hydrolase (XTH/XET, EC 2.4.1.207) activity, which transfers xyloglucanosyl residues from xyloglucan (XG) to XG-derived oligosaccharides (XGOs), a glycosyl transfer from XG to SR-labeled cellooligosaccharides and laminarioligosaccharides has been detected. The XGOs also served as acceptors for the glycosyl transfer from soluble cellulose derivatives carboxymethyl cellulose and hydroxyethylcellulose. The effectivity of these polysaccharides as glycosyl donors for transfer to XG-derived octasaccharide [1-3H]XXLGol decreased in the order XG > HEC > CMC. Isoelectric focusing in polyacrylamide gels showed that bands corresponding to hetero-transglycosylase activities coincided with zones corresponding to XTH/XET. These results can be explained as due either to substrate non-specificity of certain isoenzymes of XTH/XET or to existence of enzymes catalyzing a hetero-transfer, that is the formation of covalent linkages between different types of carbohydrate polymers.
