Crystallographic analysis of the catalytic mechanism of haloalkane dehalogenase.
Crystal structures of haloalkane dehalogenase were determined in the presence of the substrate 1,2-dichloroethane. At pH 5 and 4 degrees C, substrate is bound in the active site without being converted; warming to room temperature causes the substrate's carbon-chlorine bond to be broken, producing a chloride ion with concomitant alkylation of the active-site residue Asp124. At pH 6 and room temperature the alkylated enzyme is hydrolysed by a water molecule activated by the His289-Asp260 pair in the active site. These results show that catalysis by the dehalogenase proceeds by a two-step mechanism involving an ester intermediate covalently bound at Asp124.
BIOSON Research Institute and Laboratory of Biophysical Chemistry, University of Groningen, The Netherlands.
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D002384:Catalysis; D003001:Cloning, Molecular; D003198:Computer Simulation; D005025:Ethylene Dichlorides / Q000378:metabolism; D006088:Gram-Negative Aerobic Bacteria / Q000201:enzymology / Q000235:genetics; D006863:Hydrogen-Ion Concentration; D006867:Hydrolases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006868:Hydrolysis; D013696:Temperature; D014961:X-Ray Diffraction
D005025:Ethylene Dichlorides; C024565:ethylene dichloride; D006867:Hydrolases; C046137:haloalkane dehalogenase