title: Reaction of carbon monoxide and molecular oxygen with P450terp (CYP108) and P450BM-3 (CYP102).
abstract: The kinetics and equilibrium of carbon monoxide binding and the reaction of autodecomposition of oxycomplexes of two bacterial P450s--P450BM-3 and P450terp--have been studied and compared with the corresponding properties of P450cam and some of the microsomal P450s. The second-order reaction rate constants for the reaction of P450terp and P450BM-3 with carbon monoxide in the absence of substrate at 5 degrees C were 3.6 x 10(6) and 1.6 x 10(6) M-1 s-1, respectively. The presence of the physiological substrate markedly influenced the rate of carbon monoxide binding with P450terp, decreasing the rate constant by approximately 100-fold, and did not have a significant effect on carbon monoxide binding with P450BM-3. The reaction of carbon monoxide with both cytochromes was monophasic in the absence or in the presence of substrate. The carbon monoxide binding enthalpy change was very small for P450BM-3 (-0.2 kcal mol-1) and more negative for P450terp (-3.2 kcal mol-1). The rate constants of decomposition of oxy-P450terp and oxy-P450BM-P (heme domain of P450BM-3) at 5 degrees C were 7.1 x 10(-4) and 2.5 x 10(-2) s-1, respectively. Raising the temperature to 20 degrees C resulted in 24- and 9-fold increase of decomposition of oxy-complexes of P450terp and P450BM-P, respectively. The kinetic properties of the binding reaction of diatomic gases to P450cam, P450terp, and P450BM-3 are consistent with the structures of their active sites.
authors.affiliation: Department of Biochemistry, University of Texas Southwestern Medical Center at Dallas, 75235-9038.
authors.forename: I F
authors.initials: IF
authors.lastname: Sevrioukova
authors.forename: J A
authors.initials: JA
authors.lastname: Peterson
mesh_terms: D001410:Bacillus megaterium / Q000201:enzymology; D001426:Bacterial Proteins; D001665:Binding Sites; D019475:Camphor 5-Monooxygenase; D002248:Carbon Monoxide / Q000378:metabolism*; D042926:Cytochrome P-450 CYP4A; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D007700:Kinetics; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D009251:NADPH-Ferrihemoprotein Reductase; D010100:Oxygen / Q000378:metabolism*; D011549:Pseudomonas / Q000201:enzymology; D013053:Spectrophotometry; D013816:Thermodynamics
chemical_list: D001426:Bacterial Proteins; D002248:Carbon Monoxide; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; C073494:terpineol hydroxylase; D019475:Camphor 5-Monooxygenase; D042926:Cytochrome P-450 CYP4A; D009251:NADPH-Ferrihemoprotein Reductase; C052423:flavocytochrome P450 BM3 monoxygenases; D010100:Oxygen