Substrate-Assisted Catalysis Unifies Two Families of Chitinolytic Enzymes
详细信息 查看全文
- 作者：Ivo Tews ; Anke C. Terwisscha van Scheltinga ; Anastassis Perrakis ; Keith S. Wilson ; and Bauke W. Dijkstra
- 刊名：Journal of the American Chemical Society
- 出版年：1997
- 出版时间：August 27, 1997
- 年：1997
- 卷：119
- 期：34
- 页码：7954 - 7959
- 全文大小：309K
- 年卷期：v.119,no.34(August 27, 1997)
- ISSN：1520-5126
文摘
Hen egg-white lysozyme has long been the paradigm for enzymaticglycosyl hydrolysis with retention ofconfiguration, with a protonated carboxylic acid and a deprotonatedcarboxylate participating in general acid-basecatalysis. In marked contrast, the retaining chitin degradingenzymes from glycosyl hydrolase families 18 and 20 allhave a single glutamic acid as the catalytic acid but lack anucleophile on the enzyme. Both families have acatalytic(
)8-barrel domain in common. X-ray structures ofthree different chitinolytic enzymes complexed withsubstratesor inhibitors identify a retaining mechanism involving a protein acidand the carbonyl oxygen atom of the substrate'sC2 N-acetyl group as the nucleophile. These studiesunambiguously demonstrate the distortion of the sugar ringtoward a sofa conformation, long postulated as being close to that ofthe transition state in glycosyl hydrolysis.
)8-barrel domain in common. X-ray structures ofthree different chitinolytic enzymes complexed withsubstratesor inhibitors identify a retaining mechanism involving a protein acidand the carbonyl oxygen atom of the substrate'sC2 N-acetyl group as the nucleophile. These studiesunambiguously demonstrate the distortion of the sugar ringtoward a sofa conformation, long postulated as being close to that ofthe transition state in glycosyl hydrolysis.