Abstract

An enzyme preparation that catalyzes the degradation of xyloglucan was obtained by extraction of the cell walls of soybean hypocotyls with a buffer containing 1.0 M NaCl. The enzyme preparation was shown to catalyze two-step degradation of xyloglucan. The polysaccharide was first degraded into comparatively large fragments, which were then further degraded into monosaccharides. In order to elucidate the mode of degradation of the xyloglucan during cell growth, the activities of xyloglucandegrading enzymes of soybean-hypocotyl segments were assayed at different stages of elongation. The total activities of the degrading enzymes were lower in the elongating regions than in the non-elongating regions. However, high levels of endo-β-l,4-glucanase were found in the elongating regions. These results suggest that xyloglucan is hydrolyzed by endo-β-1,4-glucanase into comparatively large fragments at the initial stage of growth and the resulting fragments are further degraded into monosaccharides during cell elongation.

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