ISOLATION OF BETA-GALACTOSIDASE FRACTIONS FROM JAPANESE PEAR - ACTIVITY AGAINST NATIVE CELL-WALL POLYSACCHARIDES

beta-Galactosidase (EC 3.2.1.23) was purified from the cell wall of th e fruit of Japanese pear (Pyrus serotina Rehder var. culta Rehder cv. Hosui) and characterized. Five peaks of beta-galactosidase activity, d esignated as Gal I to V, were separated by hydrophobic chromatography on butyl toyopearl and ion exchange chromatography on Mono S. These is olated beta-galactosidases were investigated with regard to their abil ities to release monomeric galactose from the fractionated polymers of native cell wall (cyclo-hexane-trans-1,2-diamine tetraacetic acid-, N a2CO3-, guanidine thiocyanate- and KOH-soluble fractions) and arabinog alactan (from larch wood). All the beta-galactosidase fractions were a ctive against native cell wall polysaccharides although to varying deg rees. Gal I reacted to all fractions of native cell wall and arabinoga lactan. Gal II released much galactose only from KOH-soluble polymers and arabinogalactan. Gal III released the most galactose, from cyclohe xane-trans-1,2-diamine tetraacetic acid-, Na2CO3- and guanidine thiocy anate-soluble cell wall polymers which probably contained galactosyl s ide chains of pectic polymers, although it did not react much to arabi nogalactan. In addition, the activity of Gal III dramatically increase d as ripening proceeded. Furthermore, Gal III was purified to homogene ity by gel filtration on TSKgel 3000SW and the size of a polypeptide w as 80 kDa on SDS-PAGE.