title: Affinity labeling of catechol O-methyltransferase by N-haloacetyl derivatives of 3,5-dimethoxy-4-hydroxyphenylethylamine and 3,4-dimethoxy-5-hydroxyphenylethylamine. Kinetics of inactivation.
abstract: In an attempt to elucidate the relationship between the chemical structure and the catalytic function of catechol O-methyltransferase (COMT), several classes of affinity labeling reagents have been synthesized and their interaction with COMT has been studied. Earlier studies have shown that various N-haloacetyl derivatives of 3,5-dimethoxy-4-hydroxyphenylethylamine were effective affinity labeling reagents for this enzyme. In this report we have shown that N-haloacetyl derivatives of the isomeric 3,4-dimethoxy-5-hydroxyphenylethylamine also rapidly and irreversibly inactivate COMT ant they satisfy many of the criteria established for affinity labeling reagents. This latter group of agents appear to modify a nucleophilic residue at the active site of COMT different from that modified by the 3,5-dimethoxy-4-hydroxyphenylethylamine series. Evidence to support this conclusion has been obtained by comparing the kinetics of COMT inactivation and the substrate protection profiles for these two classes of affinity labeling reagents.
mesh_terms: D000818:Animals; D001665:Binding Sites; D002394:Catechol O-Methyltransferase / Q000302:isolation & purification*; D006863:Hydrogen-Ion Concentration; D007461:Iodoacetates / Q000494:pharmacology; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D008297:Male; D008433:Mathematics; D010627:Phenethylamines / Q000138:chemical synthesis / Q000494:pharmacology; D011485:Protein Binding; D011487:Protein Conformation; D051381:Rats; D012436:S-Adenosylmethionine / Q000494:pharmacology
chemical_list: D007461:Iodoacetates; D010627:Phenethylamines; D012436:S-Adenosylmethionine; D002394:Catechol O-Methyltransferase