title: Exchange of free and bound coenzyme of flavin enzymes studied with [14C]FAD.
abstract: The exchange of bound FAD for free FAD was studied with D-amino acid oxidase (D-amino acid:oxygen oxidoreductase (deaminating), EC 1.4.3.3) and beta-D-glucose oxidase (beta-D-glucose:oxygen 1-oxidoreductase, EC 1.1.3.4). For a simple measurement of the reaction rate, equimolar amounts of the enzyme and [14C]FAD were mixed. The exchange occurred very rapidly in the holoenzyme of D-amino acid oxidase at 25 degrees C, pH 8.3 (half life of the exchange: 0.8 min), but slowly in the presence of the substrate or a competitive inhibitor, benzoate. It also occurred slowly in the purple complex of D-amino acid oxidase. In the case of beta-D-glucose oxidase, however, the exchange occurred very slowly at 25 degrees C, pH 5.6, regardless of the presence of the substrate or p-chloromercuribenzoate. On the basis of these findings, the turnover of the coenzymes of flavin enzymes in mammals is discussed.
mesh_terms: D000818:Animals; D003605:D-Amino-Acid Oxidase / Q000378:metabolism*; D005182:Flavin-Adenine Dinucleotide / Q000302:isolation & purification / Q000378:metabolism*; D005949:Glucose Oxidase / Q000378:metabolism*; D006207:Half-Life; D007668:Kidney / Q000032:analysis; D007700:Kinetics; D008099:Liver / Q000032:analysis; D008433:Mathematics; D051381:Rats; D013552:Swine
chemical_list: D005182:Flavin-Adenine Dinucleotide; D005949:Glucose Oxidase; D003605:D-Amino-Acid Oxidase