[Show abstract][Hide abstract] 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.
The Protein Journal 12/2008; 27(7-8):434-9. · 1.13 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Conformational and structural changes of lentil seedlings amine oxidase (LSAO) were studied in the presence of trifluoroethanol (TFE) by spectroscopic and analytical techniques. At TFE concentrations up to 5%, the induction of a structural transition from beta-sheet to alpha-helix and up to 10% TFE a structural transition from alpha-helix to beta-sheet as well as inactivation of the enzyme are observed. At TFE concentrations between 10-35%, LSAO proves to be prone to aggregation and beyond 35% TFE leads to a non-native protein structure with a high alpha-helix content. The obtained results revealed that the aggregation of LSAO is strongly linked to the nature of secondary structures.
Protein and Peptide Letters 02/2008; 15(5):521-7. · 1.99 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Here we report the cDNA nucleotide sequences of a calmodulin-binding catalase and an antiquitin from the latex of the Mediterranean shrub Euphorbia characias. Present findings suggest that catalase and antiquitin might represent additional nodes in the Euphorbia defense systems, and a multi-enzymatic interaction contributing to plant's protection against biotic and abiotic stresses is proposed to occur in E. characias laticifers.
[Show abstract][Hide abstract] ABSTRACT: Polyketone polymer -[-CO-CH(2)-CH(2)-](n)-, obtained by copolymerization of ethene and carbon monoxide, is utilized for immobilization of three different enzymes, one peroxidase from horseradish (HRP) and two amine oxidases, from bovine serum (BSAO) and lentil seedlings (LSAO). The easy immobilization procedure is carried out in diluted buffer, at pH 7.0 and 3 degrees C, gently mixing the proteins with the polymer. No bifunctional reagents and spacer arms are required for the immobilization, which occurs exclusively via a large number of hydrogen bonds between the carbonyl groups of the polymer and the -NH groups of the polypeptidic chain. Experiments demonstrate a high linking capacity of polymer for BSAO and an extraordinary strong linkage for LSAO. Moreover, activity measurements demonstrate that immobilized LSAO totally retains the catalytic characteristics of the free enzyme, where only a limited increase of K(M) value is observed. Finally, the HRP-activated polymer is successfully used as active packed bed of an enzymatic reactor for continuous flow conversion and flow injection analysis of hydrogen peroxide containing solutions.
Journal of Biotechnology 02/2007; 127(4):670-8. · 3.18 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The thermal stability of copper/quinone containing amine oxidases from Euphorbia characias latex (ELAO) and lentil seedlings (LSAO) was measured in 100 mM potassium phosphate buffer (pH 7.0) following changes in absorbance at 292 nm. ELAO was shown to be about 10 degrees C more stable than LSAO. The dissociative thermal inactivation of ELAO was studied using putrescine as substrate at different temperatures in the range 47-70 degrees C, and a "conformational lock" was developed using the theory pertaining to oligomeric enzyme. Moreover ELAO was shown to be more stable towards denaturants than LSAO, as confirmed by dodecyl trimethylammonium bromide denaturation curves. A comparison of the numbers of contact sites in inter-subunits of ELAO relative to LSAO led us to conclude that the higher stability of ELAO to temperature and towards denaturants was due to the presence of larger number of contact sites in the conformational lock of the enzyme. This study also gives a putative common mechanism for thermal inactivation of amine oxidases and explains the importance of C-terminal conserved amino acids residues in this class of enzymes.
The Protein Journal 05/2005; 24(3):183-91. · 1.13 Impact Factor