Stereochemistry of chitin hydrolysis by a plant chitinase/lysozyme and X-ray structure of a complex with allosamidin: evidence for substrate assisted catalysis.
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 ...
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.
Related Citations:
Crystal Structures of Hevamine, a Plant Defence Protein with Chitinase and Lysozyme Activity, and its Complex with an Inhibitor Terwisscha Van Scheltinga, A.C., Kalk, K.H., Beintema, J.J., Dijkstra, B.W. (1994) Structure 2: 1181
Crystallization of Hevamine, an Enzyme with Lysozyme(Slash)Chitinase Activity from Hevea Brasiliensis Latex Rozeboom, H.J., Budiani, A., Beintema, J.J., Dijkstra, B.W. (1990) J Mol Biol 212: 441
Organizational Affiliation:
BIOSON Research Institute, University of Groningen, The Netherlands.
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