Reversible thermal inactivation and conformational states in denaturant guanidinium of a calcium-dependent peroxidase from Euphorbia characias.
The changes in the heme environment and overall structure occurring during reversible thermal inactivation and in denaturant guanidinium of Euphorbia characias latex peroxidase (ELP) were investigated in the presence and absence of calcium ions. Native active enzyme had an absorption spectrum typical of a quantum-mixed spin ferric heme protein. After 40 min at 60 degrees C ELP was fully inactivated showing the spectroscopic behavior of a pure hexacoordinate low-spin protein. The addition of Ca2+ to the thermally inactivated enzyme restored its native activity and its spectroscopic features, but did not increase the stability of the protein in guanidinium. It is concluded that, in Euphorbia peroxidase, Ca2+ ion play a key role in conferring structural stability to the heme environment and in retaining active site geometry.
Mura
Anna
A
Department of Applied Sciences in Biosystems, University of Cagliari, I-09042 Monserrato, CA, Italy.
Longu
Silvia
S
Padiglia
Alessandra
A
Rinaldi
Andrea C
AC
Floris
Giovanni
G
Medda
Rosaria
R
D002118:Calcium / Q000737:chemistry*; D004789:Enzyme Activation; D004795:Enzyme Stability; D028481:Euphorbia / Q000201:enzymology*; D019791:Guanidine / Q000737:chemistry; D006418:Heme / Q000737:chemistry*; D007700:Kinetics; D009195:Peroxidase / Q000737:chemistry* / Q000302:isolation & purification; D010940:Plant Proteins / Q000737:chemistry* / Q000302:isolation & purification; D011487:Protein Conformation; D011489:Protein Denaturation; D013696:Temperature
D010940:Plant Proteins; D006418:Heme; D009195:Peroxidase; D019791:Guanidine; D002118:Calcium