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Kinetic and spectral properties of pea cytosolic ascorbate peroxidase
Author(s) -
Marquez Leah A.,
Quitoriano Mannix,
Zilinskas Barbara A.,
Dunford H.Brian
Publication year - 1996
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(96)00562-5
Subject(s) - peroxidase , cytochrome c peroxidase , chemistry , porphyrin , yeast , reaction rate constant , enzyme , cytosol , cytochrome c , kinetics , photochemistry , stereochemistry , biochemistry , mitochondrion , physics , quantum mechanics
Sufficient highly purified native pea cytosolic ascorbate peroxidase was obtained to characterize some of its kinetic and spectral properties. Its rate constant for compound I formation from reaction with H 2 O 2 is 4.0 × 10 7 M −1 s −1 , somewhat faster than is typical for peroxidases. Compound I has the typical optical spectrum of an iron(IV)‐porphyrin‐π‐cation radical, despite considerable homology with yeast cytochrome c peroxidase. The rate constant for compound I reduction by ascorbate is extremely fast (8.0 × 10 7 M −1 s −1 at pH 7.8), again in marked contrast to the behavior of the yeast enzyme. The pH‐rate profile for compound I formation indicates a p K a value of 5.0 for a group affecting the active site reaction.