title: [Study of the kinetic mechanism of the pyruvate-2,6-dichlorophenolindophenol reductase activity of muscle pyruvate dehydrogenase].
abstract: The mechanism of pyruvate-2,6-dichlorophenol-indophenol (2,6-CPI) reductase reaction catalyzed by the pyruvate dehydrogenase complex from pigeon breast muscle and by its pyruvate dehydrogenase component was studied. The K'm values for 2,6-DCPI in both cases were found equal to 1.3--1.4-10(-5) M. The double reverse values plots obtained at a fixed concentration of the first substrate and a variable concentration of the second one were linear and had a constant K'm/V'max ratio. The substitution of thiamine pyrophosphate and pyruvate by the substrate decarboxylation product, i.e. 2-oxyethyl thiamine pyrophosphate under similar conditions resulted in kinetic plots, typical for the "ping-pong" mechanism of enzymatic reactions. A mechanism of the pyruvate 2,6-DCPI reductase reaction, providing for the interaction of 2-oxyethyl thiamine pyrophosphate after its binding to the apoenzyme with a certain protein group of the pyruvate dehydrogenase active centre, was postulated. The reaction was shown to result in the production of acetyl-substituted reduced form of the enzyme. Regeneration of free enzyme required the presence of 2,6-DCPI as oxidizing agent.
mesh_terms: D015086:2,6-Dichloroindophenol / Q000378:metabolism*; D000818:Animals; D001051:Apoenzymes / Q000378:metabolism; D001665:Binding Sites; D010856:Columbidae; D007215:Indophenol / Q000031:analogs & derivatives*; D007700:Kinetics; D009132:Muscles / Q000201:enzymology*; D011485:Protein Binding; D011768:Pyruvate Dehydrogenase Complex / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: D001051:Apoenzymes; D011768:Pyruvate Dehydrogenase Complex; D007215:Indophenol; D015086:2,6-Dichloroindophenol
vernacular_title: Izuchenie kineticheskogo mekhanizma piruvat-2,6-dikhlorfenolindofenolreduktaznoĭ aktivnosti myshechnoĭ piruvatdegidrogenazy