Reyes F, Calatayud J, Vazquez C, Martínez M J
Centro de Investigaciones Biológicas, Unidad de Microbiologia Aplicada, CSIC, Madrid, Spain.
FEMS Microbiol Lett. 1989 Nov;53(1-2):83-7. doi: 10.1016/0378-1097(89)90370-4.
A hexosaminidase from autolyzed cultures of Aspergillus nidulans was purified 196 fold and characterized as a beta-N-acetylglucosaminidase (EC 3.2.1.30). The enzyme has a MW of 190000, a pI of 4.3, and optimum pH of 5.0 and is unstable at temperatures above 50 degrees C. The enzyme is a glycoprotein with 19.5% sugars, mannose being the principal component. It binds strongly to chitin. The enzyme hydrolyzes different substrates. The Ki with the competitive inhibitor 2-acetamido-2-deoxy-D-gluconolactone was independent of the substrate used. The enzyme was inhibited by Hg2+, Ag+, acetate and other organic anions. The kinetics of hydrolysis of chitin oligosaccharides from 2 to 6 units was studied by HPLC. This enzyme is an exoenzyme which degraded chitin oligomers gradually with the production of N-acetylglucosamine. The hydrolysis of N-N'-diacetylchitobiose was inhibited non-competitively by glucosamine and N-acetylglucosamine. In mixtures of chitin oligosaccharides, the hydrolysis of chitobiose was competitively inhibited by each of the other oligomers.
从构巢曲霉自溶培养物中纯化得到一种己糖胺酶，纯化倍数为196倍，其被鉴定为β-N-乙酰氨基葡萄糖苷酶（EC 3.2.1.30）。该酶的分子量为190000，等电点为4.3，最适pH为5.0，在温度高于50℃时不稳定。该酶是一种糖蛋白，含糖量为19.5%，主要成分是甘露糖。它与几丁质有很强的结合力。该酶能水解不同的底物。竞争性抑制剂2-乙酰氨基-2-脱氧-D-葡萄糖酸内酯的Ki与所使用的底物无关。该酶受到Hg2+、Ag+、乙酸盐和其他有机阴离子的抑制。通过高效液相色谱法研究了2至6个单元的几丁质寡糖的水解动力学。这种酶是一种外切酶，它随着N-乙酰氨基葡萄糖的产生逐渐降解几丁质寡聚物。氨基葡萄糖和N-乙酰氨基葡萄糖对N-N'-二乙酰壳二糖的水解有非竞争性抑制作用。在几丁质寡糖混合物中，壳二糖的水解受到其他每种寡聚物的竞争性抑制。
