title: Chemical modification of L-lactate 2-monooxygenase with fluorodinitrobenzene: evidence for two essential histidine residues.
abstract: The modification of L-lactate 2-monooxygenase (lactate oxidase) with radioactively labeled fluorodinitrobenzene in 50 mM tris(hydroxymethyl)aminomethane (Tris)-acetate, pH 6.0, resulted in complete inactivation with the incorporation of 1 mol of dinitrophenyl per catalytic site. Analysis of acid hydrolysates using high-pressure liquid chromatography and an amino acid analyzer showed that Nim-(dinitrophenyl)histidine accounted for 95% of the incorporated label. Approximately 50% of the flavin in the modified enzyme was reduced by lactate, formed a sulfite complex, and underwent a photochemical reaction with oxalate. These results suggest that each active site in lactate oxidase contains two essential histidine residues that are modified in a mutually exclusive manner.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D002851:Chromatography, High Pressure Liquid; D004139:Dinitrofluorobenzene / Q000378:metabolism*; D006639:Histidine / Q000378:metabolism*; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D009578:Nitrobenzenes / Q000378:metabolism*; D010088:Oxidoreductases / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D009578:Nitrobenzenes; D006639:Histidine; D004139:Dinitrofluorobenzene; D006899:Mixed Function Oxygenases; D010088:Oxidoreductases; C021497:lactate 2-monooxygenase