title: The mechanism of action of ethanolamine ammonia-lyase, an adenosylcobalamin-dependent enzyme. Evidence for a carboxyl group at the active site.
abstract: Ethanolamine ammonia-lyase is an adenosylcobalamin-dependent enzyme that catalyzes the rearrangement of ethanolamine and other vicinal amino alcohols to oxo-compounds and ammonia. Treatment of this enzyme with the sulfhydryl group-blocking reagent methyl methanethiosulfonate produces a species with diminished catalytic activity. When methyl methanethiosulfonate -treated ethanolamine ammonia-lyase was incubated with a carboxyl-blocking reagent consisting of glycine ethyl ester plus a water-soluble carbodiimide, the enzyme lost more than 80% of its residual activity, while at the same time glycine ethyl ester was incorporated into it at a stoichiometry of 6 mol/mol of enzyme. Both the loss of activity and the incorporation of glycine ethyl ester were prevented if ethanolamine was included in the glycine ethyl ester-containing incubation mixture. These results suggest that an active site carboxyl group plays a role in the mechanism of catalysis by ethanolamine ammonia-lyase, and that this carboxyl group is amidated when the enzyme is incubated with glycine ethyl ester plus carbodiimide.
mesh_terms: D000642:Ammonia-Lyases / Q000378:metabolism*; D001665:Binding Sites; D003038:Cobamides / Q000378:metabolism*; D004981:Ethanolamine Ammonia-Lyase / Q000378:metabolism*; D005022:Ethyldimethylaminopropyl Carbodiimide / Q000031:analogs & derivatives / Q000494:pharmacology; D005998:Glycine / Q000031:analogs & derivatives / Q000378:metabolism; D007700:Kinetics; D008741:Methyl Methanesulfonate / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D003038:Cobamides; C014674:methyl methanethiosulfonate; C022010:glycine ethyl ester; C041829:1-ethyl-3-(3-(dimethylamino)propyl)carbodiimide methiodide; D008741:Methyl Methanesulfonate; D000642:Ammonia-Lyases; D004981:Ethanolamine Ammonia-Lyase; C000913:cobamamide; D005022:Ethyldimethylaminopropyl Carbodiimide; D005998:Glycine