Spectral characterization of cytochrome P-450 of a strain of Candida tropicalis grown on tetradecane.

Abstract

Several properties of the cytochrome P-450 induced in the yeast Candida tropicalis by growth on tetradecane have been studied by differential visible spectroscopy on microsomes. The spectral changes typical of this cytochrome have been obtained by subtraction of an unspecific spectral change, possibly due to the presence of other hemoproteins in microsomes, from the experimental difference spectra. Like the previously described cytochromes P-450 from yeast and mammalian liver, C. tropicalis cytochrome P-450 is in spin-state equilibrium at ambient temperature: about 30% of the originally low-spin cytochrome is converted to the high-spin state upon increasing the ionic strength of the medium, whereas 30% of the originally high-spin cytochrome is converted to the low-spin state upon addition of hydrophobic alcohols. C. tropicalis cytochrome P-450 readily binds nitrogenous ligands, isocyanides and phosphines in the ferric and ferrous state with spectral characteristics similar to those reported for other yeast or mammalian cytochromes P-450. It also reacts sucessively with cumylhydroperoxide and 1,3-benzodioxole to form a high-valent iron-oxo species and an iron-carbene metabolite complex. However it fails to produce any spectral or spin-state change upon addition of hydrophobic non-coordinating compounds such as n-tetradecane, its substrate in vivo.