Kinetic and spectral properties of pea cytosolic ascorbate peroxidase

FEBS Letters

Dunford, H.Brian¹  Zilinskas, Barbara A.²  Marquez, Leah A.¹  Quitoriano, Mannix² 

[1] Department of Chemistry, University of Alberta, Edmonton, Alta., Canada T6G 2G2;Department of Plant Science, Cook College, Rutgers University, New Brunswick, NJ 08903-0231, USA

关键词: Compound I;    Compound II;    Transient state kinetics;    Optical spectra;    Ascorbate oxidation;    pH dependence;    Cytochrome c peroxidase;    comparison;   

DOI  :  10.1016/0014-5793(96)00562-5

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

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 H₂O₂ is 4.0 × 10⁷ 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 × 10⁷ 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 pK _a value of 5.0 for a group affecting the active site reaction.

【 授权许可】

Unknown