Department of Chemistry, Campus Box 215, University of Colorado, Boulder, Colorado 80309.
Plant Physiol. 1984 Jan;74(1):52-60. doi: 10.1104/pp.74.1.52.
Heat-labile elicitors of phytoalexin accumulation in soybeans (Glycine max L. Merr. cv Wayne) were detected in culture filtrates of Erwinia carotovora grown on a defined medium containing citrus pectin as the sole carbon source. The heat-labile elicitors were highly purified by cation-exchange chromatography on a CM-Sephadex (C-50) column, followed by agarose-affinity chromatography on a Bio-Gel A-0.5m gel filtration column. The heat-labile elicitor activity co-purified with two alpha-1,4-endopolygalacturonic acid lyases (EC 4.2.2.2). Endopolygalacturonic acid lyase activity appeared to be necessary for elicitor activity because heat-inactivated enzyme preparations did not elicit phytoalexins. The purified endopolygalacturonic acid lyases elicited pterocarpan phytoalexins at microbial-inhibitory concentrations in the soybean-cotyledon bioassay when applied at a concentration of 55 nanograms per milliliter (1 x 10(-9) molar). One of these lyases released heat-stable elicitors from soybean cell walls, citrus pectin, and sodium polypectate. The heat-stable elicitor-active material solubilized from soybean cell walls by the lyase was composed of at least 90% (w/v) uronosyl residues. These results demonstrate that endopolygalacturonic acid lyase elicits phytoalexin accumulation by releasing fragments from pectic polysaccharides in plant cell walls.
热不稳定的植物抗毒素积累诱导物在以柑橘果胶为唯一碳源的限定培养基中生长的欧文氏菌（Erwinia carotovora）的培养滤液中被检测到。热不稳定的诱导物通过阳离子交换色谱在 CM-Sephadex（C-50）柱上高度纯化，然后通过琼脂糖亲和色谱在 Bio-Gel A-0.5m 凝胶过滤柱上进一步纯化。热不稳定的诱导物活性与两种α-1,4-内切多聚半乳糖醛酸裂解酶（EC 4.2.2.2）共同纯化。内切多聚半乳糖醛酸裂解酶活性似乎是诱导物活性所必需的，因为热失活的酶制剂不能诱导植物抗毒素。纯化的内切多聚半乳糖醛酸裂解酶在大豆子叶生物测定中以微生物抑制浓度应用时，在 55 纳克/毫升（1 x 10(-9)摩尔）的浓度下诱导出紫檀烷类植物抗毒素。其中一种裂解酶从大豆细胞壁、柑橘果胶和聚半乳糖酸钠中释放出热稳定的诱导物。该裂解酶从大豆细胞壁中溶解的热稳定诱导物活性物质至少由 90%（w/v）的糖醛酸残基组成。这些结果表明，内切多聚半乳糖醛酸裂解酶通过从植物细胞壁中的果胶多糖中释放片段来诱导植物抗毒素的积累。
