Bishop P D, Pearce G, Bryant J E, Ryan C A
J Biol Chem. 1984 Nov 10;259(21):13172-7.
Mild acid hydrolysis of a small (Mr = 6 kDa) pectic polysaccharide isolated from tomato leaves, an inducer of the synthesis and accumulation of two proteinase inhibitors in excised tomato plants, yielded a alpha-D-polygalacturonic acid polymer with degree of polymerization = 20 that retained proteinase inhibitor-inducing activity. Enzymic and acid hydrolysis of this polygalacturonan yielded a series of alpha-1,4-D-galacturonic acid oligomers with degrees of polymerization from 2 to 6 which were purified to homogeneity and assayed for proteinase inhibitor-inducing activity in young excised tomato plants. All of the oligomers exhibited activity. The hexagalacturonide possessed the highest activity and the trimer the lowest. The evidence supports a possible role for plant cell wall fragments as systemic messengers that regulate the expression of proteinase inhibitor genes in plant leaves in response to pest attacks.
从番茄叶片中分离出一种小的（Mr = 6 kDa）果胶多糖，它是离体番茄植株中两种蛋白酶抑制剂合成和积累的诱导剂，对其进行温和酸水解，得到一种聚合度为20的α-D-聚半乳糖醛酸聚合物，该聚合物保留了蛋白酶抑制剂诱导活性。对这种聚半乳糖醛酸进行酶解和酸水解，得到一系列聚合度为2至6的α-1,4-D-半乳糖醛酸寡聚物，将其纯化至同质，并在离体的幼嫩番茄植株中检测其蛋白酶抑制剂诱导活性。所有寡聚物均表现出活性。六聚半乳糖醛酸的活性最高，三聚体的活性最低。这一证据支持了植物细胞壁片段可能作为系统信使的作用，它们可响应害虫攻击调节植物叶片中蛋白酶抑制剂基因的表达。
