title: Absorption spectra of highly purified liver microsomal cytochrome P-450 in non-equilibrium conformational states at low temperatures.
abstract: Absorption spectra of highly purified liver microsomal cytochrome P-450 in non-equilibrium states were obtained at 77 K by reduction with trapped electrons, formed by gamma-irradiation of the water-glycerol matrix. In contrast to the equilibrium form of ferrous cytochrome P-450 with the heme iron in the high-spin state the non-equilibrium ferrous state has a low-spin heme iron. The absorption spectrum of the non-equilibrium ferrous cytochrome P-450 is characterized by two bands at 564 (alpha-band) and 530 nm (beta-band). When the temperature is increased to about 278 K this non-equilibrium form of the reduced enzyme is relaxed to the corresponding equilibrium form with a single absorption band at 548 nm in the visible region characteristic for a high-spin heme iron.
mesh_terms: D000818:Animals; D003080:Cold Temperature; D003577:Cytochrome P-450 Enzyme System; D008862:Microsomes, Liver / Q000201:enzymology*; D011487:Protein Conformation; D011817:Rabbits; D013053:Spectrophotometry
chemical_list: D003577:Cytochrome P-450 Enzyme System