Biopolymer Research Unit, National Center for Agricultural Utilization Research, Agricultural Research Service, U.S. Department of Agriculture, 1815 North University Street, Peoria, Illinois 61604.
Appl Environ Microbiol. 1991 Sep;57(9):2523-8. doi: 10.1128/aem.57.9.2523-2528.1991.
A xanthanase complex secreted by a consortium of heat-stable, salt-tolerant bacteria includes a lyase that specifically removes terminal pyruvated beta-d-mannose residues from the side chains of xanthan gum. The enzyme was purified to homogeneity from the culture broth following ion-exchange chromatography and gel permeation chromatography. It consists of a single subunit of molecular weight 33,000. The enzyme is stable to 55 degrees C for more than 6 h in 20 mM sodium phosphate buffer (pH 5.0) containing 0.25 M NaCl. Optimal enzyme activity was observed at 0.05 M NaCl and a pH of 5. The enzyme has a pI of 3.7. It does not remove unsubstituted terminal beta-d-mannose residues from xanthan side chains nor does it hydrolyze p-nitrophenyl-beta-d-mannose. Treatment of xanthan with purified lyase results in a polysaccharide containing side chains terminating in an unsaturated 4,5-ene-glucuronic acid.
由耐热耐盐细菌组成的协同菌分泌出 xanthanase 复合酶，其中包含一种裂解酶，它能特异性地从黄原胶侧链上去除末端丙酮酸β-d-甘露糖残基。该酶可通过离子交换层析和凝胶渗透层析从发酵液中纯化为均相。它由分子量为 33000 的单一亚基组成。在 20 mM 磷酸钠缓冲液（pH 5.0）中，该酶在 55°C 下稳定超过 6 小时，缓冲液中含有 0.25 M NaCl。在 0.05 M NaCl 和 pH 值为 5 的条件下观察到最佳酶活性。该酶的等电点为 3.7。它不能从黄原胶侧链上去除未取代的末端β-d-甘露糖残基，也不能水解对硝基苯基-β-d-甘露糖。用纯化的裂解酶处理黄原胶会导致多糖侧链末端形成不饱和 4,5-烯-葡萄糖醛酸。
Zotero 插件