Terwisscha van Scheltinga A C, Armand S, Kalk K H, Isogai A, Henrissat B, Dijkstra B W
BIOSON Research Institute, University of Groningen, The Netherlands.
Biochemistry. 1995 Dec 5;34(48):15619-23. doi: 10.1021/bi00048a003.
The plant enzyme hevamine has both chitinase and lysozyme activity. HPLC analysis of the products of the hydrolysis of chitopentaose shows that hevamine acts with retention of the configuration, despite the absence of a nucleophilic or stabilizing carboxylate. To analyze the stabilization of a putative oxocarbonium ion intermediate, the X-ray structure of hevamine complexed with the inhibitor allosamidin was determined at 1.85 A resolution. This structure supports the role of Glu127 as a proton donor. The allosamizoline group binds in the center of the active site, mimicking a reaction intermediate in which a positive charge at C1 is stabilized intramolecularly by the carbonyl oxygen of the N-acetyl group at C2.
植物酶橡胶树几丁质酶兼具几丁质酶和溶菌酶活性。对壳五糖水解产物的高效液相色谱分析表明，尽管缺乏亲核或稳定的羧酸盐，但橡胶树几丁质酶作用时构型得以保留。为分析假定的氧鎓离子中间体的稳定性，以1.85埃的分辨率测定了与抑制剂别苦杏仁苷复合的橡胶树几丁质酶的X射线结构。该结构支持了Glu127作为质子供体的作用。别苦杏仁唑啉基团结合在活性位点中心，模拟了一种反应中间体，其中C1处的正电荷通过C2处N - 乙酰基的羰基氧在分子内得到稳定。
