Département de Biochimie, Faculté de Médecine, Université de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada.
Appl Environ Microbiol. 1990 Apr;56(4):844-8. doi: 10.1128/aem.56.4.844-848.1990.
Bacillus megaterium P1, a bacterial strain capable of hydrolyzing chitosan, was isolated from soil samples. Chitosan-degrading activity was induced by chitosan but not by its constituent d-glucosamine. Extracellular secretion of chitosanase reached levels corresponding to 1 U/ml under optimal conditions. Three chitosan-degrading proteins (chitosanases A, B, and C) were purified to homogeneity. Chitosanase A (43 kilodaltons) was highly specific for chitosan and represented the major chitosan-hydrolyzing species. Chitosanases B (39.5 kilodaltons) and C (22 kilodaltons) corresponded to minor activities and possessed comparable specific activities toward chitosan, chitin, and cellulose. Chitosanase A was active from pH 4.5 to 6.5 and was stable on the basis of activity up to 45 degrees C. The optimum temperature for enzymatic chitosan hydrolysis was 50 degrees C. Kinetic studies on chitosanase A suggest that the enzyme is substrate inhibited. The apparent K(m) and V(max) determined at 22 degrees C and pH 5.6 were 0.8 mg/ml and 280 U/mg, respectively. End products of chitosan hydrolysis by each of the three chitosanases were identified as glucosamine oligomers, similar to those obtained for previously reported chitosanase digestions.
从土壤样本中分离出一种能够水解壳聚糖的巨大芽孢杆菌 P1 菌株。壳聚糖降解活性是由壳聚糖诱导的，而不是由其组成成分 D-葡萄糖胺诱导的。在最佳条件下，壳聚糖酶的胞外分泌水平达到了 1 U/ml。三种壳聚糖降解蛋白（壳聚糖酶 A、B 和 C）被纯化为均一性。壳聚糖酶 A（43 千道尔顿）对壳聚糖具有高度特异性，是主要的壳聚糖水解酶。壳聚糖酶 B（39.5 千道尔顿）和 C（22 千道尔顿）对应于较小的活性，对壳聚糖、几丁质和纤维素具有可比的比活性。壳聚糖酶 A 在 pH4.5 到 6.5 之间具有活性，在 45°C 下基于活性稳定。酶法水解壳聚糖的最适温度为 50°C。壳聚糖酶 A 的动力学研究表明，该酶受到底物抑制。在 22°C 和 pH5.6 下确定的表观 K(m)和 V(max)分别为 0.8mg/ml 和 280U/mg。三种壳聚糖酶中每一种的壳聚糖水解的末端产物均鉴定为葡萄糖胺低聚物，与先前报道的壳聚糖酶消化产物相似。
