title: Activity and structural changes of Euphorbia characias peroxidase in the presence of trifluoroethanol.
abstract: Activity assays, conformational changes and transitional switches between secondary structures of a peroxidase from Euphorbia characias were studied in the presence of trifluoroethanol and in the presence or absence of calcium ions. The addition of trifluoroethanol up to 10-20% first induced a drastic decrease of alpha-helix content followed by an increase of tryptophan fluorescence emission intensity, a progressive re-induction of the formation of alpha-helical elements concomitant with loss of enzyme activity. In the presence of calcium ions, the fluorescence of the enzyme almost remained unchanged in the trifluoroethanol concentration range 5-20%. Further increase in trifluoroethanol concentration led to a protein structure characterized by a progressive re-induction of alpha-helical elements, a remarkable increase of the tryptophan fluorescence and a loss of enzyme activity. These results indicate that calcium ions in Euphorbia peroxidase play an essential role in maintaining the hydrophobic interactions on the protein structure preserving enzymatic activity.
authors.affiliation: Department of Applied Sciences in Biosystems, University of Cagliari Cittadella Universitaria, 09042 Monserrato, CA, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Pintus
authors.forename: A
authors.initials: A
authors.lastname: Mura
authors.forename: A C
authors.initials: AC
authors.lastname: Rinaldi
authors.forename: A
authors.initials: A
authors.lastname: Contini
authors.forename: D
authors.initials: D
authors.lastname: Spanò
authors.forename: R
authors.initials: R
authors.lastname: Medda
authors.forename: G
authors.initials: G
authors.lastname: Floris
mesh_terms: D002118:Calcium / Q000494:pharmacology; D002942:Circular Dichroism; D028481:Euphorbia / Q000201:enzymology*; D010544:Peroxidases / Q000737:chemistry / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism; D017433:Protein Structure, Secondary; D013050:Spectrometry, Fluorescence; D014270:Trifluoroethanol / Q000494:pharmacology*
chemical_list: D010940:Plant Proteins; D014270:Trifluoroethanol; D010544:Peroxidases; D002118:Calcium