title: Kinetic studies on reduction of cytochromes P-450 and b5 by dithionite.
abstract: The kinetics of reduction of cytochromes P-450 and b5 by dithionite had been studied in solution and in microsomal and proteoliposomal membranes by the stopped-flow technique. In all the cases studied the kinetic curves of reduction of cytochrome b5 obey first-order kinetics in relation to cytochrome with the rate constant about 14 s-1 at 10.6 mM dithionite. The kinetic curves of reduction of cytochrome P-450 fit an equation for the sum of two exponentials with the parameters varying from system to system. The simple first-order kinetics of cytochrome P-450 reduction had been observed in the presence of non-ionic detergent Triton N-101. The apparent biphasity of cytochrome P-450 reduction by dithionite should be the result asymmetric distribution of hemoprotein in microsomal and proteoliposomal membranes as well as in cytochrome oligomers in solution.
mesh_terms: D000818:Animals; D055598:Chemical Phenomena; D002621:Chemistry; D003577:Cytochrome P-450 Enzyme System; D003573:Cytochrome b Group; D015786:Cytochromes b5; D004227:Dithionite; D066298:In Vitro Techniques; D007700:Kinetics; D008081:Liposomes; D008862:Microsomes, Liver / Q000201:enzymology; D010084:Oxidation-Reduction; D011510:Proteolipids; D011817:Rabbits; D051381:Rats; D012996:Solutions; D013447:Sulfites; D013816:Thermodynamics
chemical_list: D003573:Cytochrome b Group; D008081:Liposomes; D011510:Proteolipids; D012996:Solutions; D013447:Sulfites; D004227:Dithionite; D015786:Cytochromes b5; D003577:Cytochrome P-450 Enzyme System