Vegetable Crops Department, University of Florida, Institute of Food and Agricultural Sciences, Gainesville, Florida 32611.
Plant Physiol. 1984 Aug;75(4):891-4. doi: 10.1104/pp.75.4.891.
Cell wall isolated from pericarp of normal tomato (Lycopersicon esculentum Mill. cv ;Rutgers') fruit released pectic polymers in a reaction apparently mediated by wall-bound polygalacturonase that appears with the onset of ripening. Release was negligible in wall preparations from normal green and the ripening mutant rin fruit. Pectin solubilization was most extensive at pH 2.5 with a less significant peak at 5.5. Brief exposure to low (1.5) or high (7.5) pH resulted in reduction of autolytic activity, which was also inhibited by high temperature, Ca(2+), and treatments employed to dissociate protein from cell wall. Uronic acid solubilization was significantly enhanced by 150 millimolar NaCl and by increasing temperature within the physiological range. These data indicate that the release of polyuronide from isolated cell walls is enzymic and may provide a convenient and reliable system for the study of softening metabolism.
从正常番茄（Lycopersicon esculentum Mill. cv；Rutgers'）果皮中分离得到的细胞壁在反应中释放出果胶聚合物，该反应显然由壁结合的多聚半乳糖醛酸酶介导，该酶在成熟开始时出现。在正常绿色和成熟突变体 rin 果实的细胞壁制剂中，释放量可忽略不计。在 pH 值为 2.5 时，果胶的溶解度最大，在 pH 值为 5.5 时出现较小的峰值。短暂暴露于低（1.5）或高（7.5）pH 值会导致自溶活性降低，高温、Ca(2+)和用于将蛋白质从细胞壁上分离的处理也会抑制自溶活性。150 毫摩尔氯化钠和生理范围内升高温度显著增强了糖醛酸的溶解。这些数据表明，从分离的细胞壁中释放聚半乳糖醛酸是酶促的，可能为软化代谢的研究提供一个方便可靠的系统。
