Vathipadiekal Vinod, Verma Anamika, Rao Mala
Division of Biochemical Sciences, National Chemical Laboratory, Pune 41108, India.
Biol Chem. 2007 Jan;388(1):61-5. doi: 10.1515/BC.2007.007.
This is the first report describing the enhancement of xylanase activity by the neutral amino acid glycine. Xylanase activity is increased seven-fold at alkaline pH in the presence of glycine and its pH optimum is shifted from pH 7 to 8 without using any protein engineering techniques. Analysis of the steady-state kinetics revealed that glycine in the reaction mixture increases the K(m) and k(cat) values of the enzyme. Chemoaffinity labeling and studies using glycine esters indicate an involvement of the carboxylate ion of glycine in enhancing xylanase catalytic activity. A novel possible mechanism for the glycine-assisted catalytic action of xylanase is proposed.
这是首篇描述中性氨基酸甘氨酸提高木聚糖酶活性的报告。在甘氨酸存在的情况下，木聚糖酶活性在碱性pH条件下提高了7倍，且其最适pH从pH 7转变为pH 8，而未使用任何蛋白质工程技术。稳态动力学分析表明，反应混合物中的甘氨酸会提高该酶的米氏常数（K(m)）和催化常数（k(cat)）。化学亲和标记以及使用甘氨酸酯的研究表明，甘氨酸的羧酸根离子参与提高木聚糖酶的催化活性。本文提出了一种关于甘氨酸辅助木聚糖酶催化作用的全新可能机制。
