title: Antagonistic effects of hydrostatic pressure and osmotic pressure on cytochrome P-450cam spin transition.
abstract: The combined effects of hydrostatic pressure and osmotic pressure, generated by polyols, on the spin equilibrium of fenchone-bound cytochrome P-450cam were investigated. Hydrostatic pressure indices a high spin to low spin transition, whereas polyols induce the reversed reaction. Of the four solutes used, glycerol, glucose, stachyose, and sucrose, only the last two would act on the spin transition by osmotic stress. The spin volume changes measured by both techniques are different, 29 and -350 ml/mol for hydrostatic pressure and osmotic pressure, respectively. It suggests that even if the two are perturbing water molecules, different properties are probed. From the volume change induced by osmotic stress, 19 water molecules are deduced that would be implicated in the spin transition of the fenchone-bound protein. This result suggests that water molecules other than the well defined ones located in the active site play a key role in modulating the spin equilibrium of cytochrome P-450cam.
authors.affiliation: INSERM-INRA U310, Institut de Biologie Physico-Chimique, Paris, France.
authors.forename: C
authors.initials: C
authors.lastname: Di Primo
authors.forename: E
authors.initials: E
authors.lastname: Deprez
authors.forename: G H
authors.initials: GH
authors.lastname: Hoa
authors.forename: P
authors.initials: P
authors.lastname: Douzou
mesh_terms: D019475:Camphor 5-Monooxygenase; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry* / Q000187:drug effects; D005947:Glucose / Q000494:pharmacology; D005990:Glycerol / Q000494:pharmacology; D006874:Hydrostatic Pressure; D007700:Kinetics; D006899:Mixed Function Oxygenases / Q000737:chemistry* / Q000187:drug effects; D009844:Oligosaccharides / Q000494:pharmacology; D009997:Osmotic Pressure; D016958:Pseudomonas putida / Q000201:enzymology*; D013053:Spectrophotometry; D013395:Sucrose / Q000494:pharmacology
chemical_list: D009844:Oligosaccharides; C005695:stachyose; D013395:Sucrose; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D019475:Camphor 5-Monooxygenase; D005947:Glucose; D005990:Glycerol