Studies on the acidic wall proteins that activate the wall glucanases in maize coleoptiles.

从玉米胚芽鞘细胞壁中分离纯化的胞外和胞内葡聚糖酶介导细胞壁β-(1，3)(1，4)-葡聚糖的特异性降解。我们现在认为，质外体几丁质酶可能在细胞壁葡聚糖-葡聚糖酶相互作用中发挥作用，导致这些反应的加速。从玉米胚芽鞘中分离得到的酸性壁蛋白部分具有内切几丁质酶活性。此外，这种纯化的玉米酸性几丁质酶强烈刺激内外葡聚糖酶催化β-(1，3)(1，4)-葡聚糖的水解。选定的其他来源的几丁质酶在葡聚糖酶存在下的β-葡聚糖水解中表现出类似的行为。然而，我们没有发现证据表明，在没有葡聚糖酶的情况下，几丁质酶单独对β-葡聚糖的显著水解负责。这些结果表明，壁几丁质酶(S)可能引起葡聚糖酶糖肽结构的微小但显著的变化，或者它可能作用于修饰葡聚糖结构的某些构象元件。在谷类植物中，生长素刺激细胞伸长，这一过程与细胞壁葡聚糖的代谢修饰密切相关。几丁质酶与葡聚糖酶介导的细胞壁结构变化相互作用的确切性质以及与生长素作用的关系将是未来实验的重点。

Exo- and endoglucanases purified from the cell walls of maize coleoptiles mediate a specific degradation of cell wall β-(1,3)(1,4)-glucans. We now suggest that there is a possible role for apoplastic chitinase in the cell wall glucan-glucanase interaction resulting in an acceleration of these reactions. The acidic wall protein fraction which had been isolated from maize coleoptiles is capable of endochitinase activity. Moreover, this purified maize acidic chitinase strongly stimulates both exo- and endoglucanases in catalyzing the hydrolysis of β-(1,3)(1,4)-glucans. Selected chitinases from other sources exhibited similar behavior in β-glucan hydrolysis in the presence of glucanases. However, we found no evidence to suggest that chitinases alone were responsible of significant hydrolysis of β-glucans in the absence of glucanases. These results suggest that the wall chitinase(s) may cause small but significant changes in either the glucanase glycopeptide structure or that it might act to modify certain conformational elements of the glucan structure.In cereal plants, auxin stimulates cell elongation, a process that is closely tied to metabolic modification of cell wall glucans. The precise nature of the chitinase interaction with the cell wall structural changes mediated by glucanases and the relationship to auxin action will be the focus of future experiments.