Shirai T, Ishida H, Noda J, Yamane T, Ozaki K, Hakamada Y, Ito S
Department of Biotechnology and Biomaterial Chemistry, Graduate School of Engineering, Nagoya University, Japan.
J Mol Biol. 2001 Jul 27;310(5):1079-87. doi: 10.1006/jmbi.2001.4835.
The crystal structure of the catalytic domain of alkaline cellulase K was determined at 1.9 A resolution. Because of the most alkaliphilic nature and it's highest activity at pH 9.5, it is used commercially in laundry detergents. An analysis of the structural bases of the alkaliphilic character of the enzyme suggested a mechanism similar to that previously proposed for alkaline proteases, that is, an increase in the number of Arg, His, and Gln residues, and a decrease in Asp and Lys residues. Some ion pairs were formed by the gained Arg residues, which is similar to what has been found in the alkaline proteases. Lys-Asp ion pairs are disfavored and partly replaced with Arg-Asp ion pairs. The alkaline adaptation appeared to be a remodeling of ion pairs so that the charge balance is kept in the high pH range.
碱性纤维素酶K催化结构域的晶体结构在1.9埃分辨率下得以确定。由于其极强的嗜碱性以及在pH 9.5时具有最高活性，它被商业应用于洗衣粉中。对该酶嗜碱特性的结构基础分析表明，其机制与先前针对碱性蛋白酶提出的机制相似，即精氨酸、组氨酸和谷氨酰胺残基数量增加，天冬氨酸和赖氨酸残基数量减少。一些离子对由新增的精氨酸残基形成，这与在碱性蛋白酶中发现的情况类似。赖氨酸 - 天冬氨酸离子对不受青睐，部分被精氨酸 - 天冬氨酸离子对取代。碱性适应性似乎是离子对的重塑，以便在高pH范围内保持电荷平衡。
