화학공학소재연구정보센터
Journal of Physical Chemistry B, Vol.106, No.50, 12860-12862, 2002
Fourier transform infrared evidence for a ferric six-coordinate nitrosylheme b(3) complex of cytochrome cbb(3) oxidase from Pseudomonas Stutzeri at ambient temperature
We report the first vibrational study of NO bound to an oxidized heme-copper oxidase. Cytochrome cbb(3) oxidase from P. stutzeri reduces both O-2 and NO to H2O and N2O, respectively. The ferric nitrosyl complex of cbb(3) exhibits v(N-O) at 1903 cm(-1). This frequency is very similar to v(NO) of nitric oxide reductase, the acidic form of Met Mb-NO, but 18 cm(-1) lower than that of neutral Met Mb-NO. By monitoring the NO intensity, we estimate that NO dissociates from the heme b(3) pocket, without binding to Cu-B, with k = 1.8 x 10(-3) s(-1). Therefore, NO binding occurs at the heme site and not at Cu-B, generating a nitrosonium Cu-B(1+)-NO+ species as proposed recently (Torres, J.; Cooper, C. E.; Wilson, M. T. J. Biol. Chem. 1998, 273, 87568766). The coordination of NO to cbb(3) oxidase and to nitric oxide reductase and Mb is compared and discussed.