Activity and structural changes of Euphorbia characias peroxidase in the presence of trifluoroethanol.
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.
Pintus
F
F
Department of Applied Sciences in Biosystems, University of Cagliari Cittadella Universitaria, 09042 Monserrato, CA, Italy.
Mura
A
A
Rinaldi
A C
AC
Contini
A
A
Spanò
D
D
Medda
R
R
Floris
G
G
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*
D010940:Plant Proteins; D014270:Trifluoroethanol; D010544:Peroxidases; D002118:Calcium