Mobility Limitations of Bound Polygalacturonase in Isolated Cell Wall from Tomato Pericarp Tissue

Enzymically active cell wall isolated from mature-green and ripening tomato (Lycopersicon esculentum Mill cv . `Rutgers') fruit was employed to investigate the mobility of the enzyme polygalacturonase (PG, EC 3.2.1.15). Cell walls from mature-green `Rutgers' fruit or from the ripening mutant rin, which alone exhibits little or no release of pectin, were unaffected by the addition of enzymically active cell wall from ripening `Rutgers' fruit, indicating that PG is either not transferred at all or is not transferred to sites of pectin hydrolysis. The quantity of pectin released by the addition of soluble PG to enzymically active wall depended on the quantity of enzyme added. Similar data were obtained using purified PG2. Pectin solubilization from all wall isolates exhibiting enzymically mediated pectin release diminished with time; however, transfer to fresh buffer initiated a resumption of autolytic activity, indicating that an inhibitor is released during the course of pectin hydrolysis.