α- l-Arabinofuranosidase from cell walls of Japanese pear fruits

Abstract

Cell wall-bound glycosidase activities were measured in pre-ripe and ripe fruits of Japanese pears ( Pyrus serotina Rehd. var. culta. cv. Hosui). α- l-Arabinofuranosidase (EC. 3.2.1.55) activity increased dramatically with fruit ripening and its activity was assayed during fruit development and ripening. After the fruit enlargement stage, cell wall-bound α- l-arabinofuranosidase activity increased 15-fold with fruit ripening. The enzyme was solubilized from cell walls using the chelator trans-1,2-cyclohexanediamine- N, N, N′, N′-tetraacetic acid and the solubilized enzyme purified using DEAE-cellulose, hydroxyapatite, Mono Q and Sephadex G-100 chromatography. The purified enzyme was a M r 42 000 monomer on SDS-PAGE. Optimum pH activity was 5.0 and the K m value was 34 mM for p- nitrophenyl-α- l-arabinofuranoside .