title: Yeast cytochrome P-450 catalyzing lanosterol 14 alpha-demethylation. I. Purification and spectral properties.
abstract: A form of cytochrome P-450 catalyzing lanosterol 14 alpha-demethylation (tentatively called "P-450(14)DM") was purified from microsomes of semi-anaerobically grown cells of Saccharomyces cerevisiae to gel electrophoretic homogeneity. An apparent monomeric Mr = 58,000 was estimated for the purified cytochrome by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Both optical and EPR spectra of oxidized P-450(14)DM are characteristic of low spin ferric heme proteins, and its reduced CO complex showed a Soret absorption peak at 447 nm. As in the case of hepatic microsomal cytochromes P-450, the ethyl isocyanide complex of reduced P-450(14)DM was in a pH-dependent equilibrium between two states having Soret peaks at 429 and 453 nm, the equilibrium being considerably shifted toward the 453-nm state. Oxidized P-450(14)DM was peculiar in that in its CD spectrum there was a negative shoulder at 425 nm and the 350- and 414-nm troughs possessed larger and relatively smaller [theta] values, respectively, than those reported for other low spin ferric cytochromes P-450. Lanosterol was the only compound which caused a Type I spectral change in oxidized P-450(14)DM. The lanosterol-induced low to high spin state change was, however, only slight even at saturating concentrations of the sterol, indicating that the lanosterol-P-450(14)DM adduct was in a spin state equilibrium.
mesh_terms: D000693:Anaerobiosis; D003577:Cytochrome P-450 Enzyme System / Q000302:isolation & purification* / Q000378:metabolism; D007810:Lanosterol / Q000378:metabolism*; D008861:Microsomes / Q000378:metabolism; D008970:Molecular Weight; D011489:Protein Denaturation; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D013053:Spectrophotometry
chemical_list: D007810:Lanosterol; D003577:Cytochrome P-450 Enzyme System