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The products, stoichiometry, and kinetics of the oxidation of the enzyme cytochrome P-450 cam by five polyhalomethanes and chloronitromethane are described. The reactivity of the enzyme is compared with that of deuteroheme and with the enzyme in its native cell, Pseudomonas putida (PpG-786). In all cases, the reaction entails hydrogenolysis of the carbon-halogen bond: 2FeIIP + RCXn----2FeIIIP + RCHXn-1 (P = porphyrin or P-450 cam in vitro and in vivo). Trichloronitromethane was the fastest reacting substrate, and chloroform was the slowest. The results establish that P. putida is a valid whole cell model for the reductase activity of the P-450 complement in these reactions. The reactions of cytochrome P-450 with polyhaloalkanes proceed in a manner quite analogous to other iron(II) proteins in the G conformation. The chemistry observed for the enzyme parallels that of its iron(II) porphyrin active site. Iron-bonded carbenes are not intermediates, and hydrolytically stable iron alkyls are not products of these reactions.

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Oxymyoglobin under argon reacts with NO2- and NO2 (N2O4) to produce metmyoglobin in a spectrally clean process with clear isosbestic points. In both cases, the reactant is NO2-. The second-order rate constant for NO2- or N2O4 is the same: d(Mb+)/dt = k(MbO2)(NO2-) where k = 0.21 +/- 0.02 L mol-1 S-1. The reaction of MbO2 with NO under argon is a complex process and entails the generation of Mb+ and OONO- (peroxynitrite) in the first step. The latter (lambda MAX, 302 nm) was poorly resolved from more intense protein absorption in the 300-nm region. However, at pH 9, the change in absorbance corresponded exactly to a quantitative production of the OONO-ion. Hydroxy radicals from it were trapped with ethylene-1, 2-(13) C. The initial step is followed in sequence by the rapid formation of MbNO+. The iron(III)-nitrosyl adduct hydrolyzes slowly to MbII and NO2- (k = 8.0 +/- 0.8 x 10(-5) S-1. MbII then rapidly associates with NO, and MbNO is the final product of this reaction. Oxymyoglobin is inert to NO3-. In contrast to the results under argon, in air the reactions of MbO2 with NO2-, NO, and NO2 (N2O4) all proceed in the same autocatalytic fashion with kAVE (for the autocatalytic rates) approximately equal to 9 +/- 5 L mol-1 s-1. Nitrite is the initial reactant in all cases. Isosbestic points are not observed in the visible spectrum, and additional porphyrin iron-ligated species are intermediates. Based upon work with iron porphyrins.

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