Related Experiment Video
Updated: Jul 12, 2026
A Rapid and Specific Microplate Assay for the Determination of Intra- and Extracellular Ascorbate in Cultured Cells
Published on: April 12, 2014
Kinetic and spectral properties of pea cytosolic ascorbate peroxidase
L A Marquez1, M Quitoriano, B A Zilinskas
1Department of Biochemistry, University of Alberta, Edmonton, Canada.
Abstract:
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.O x 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-pi-cation radical, despite considerable homology with yeast cytochrome c peroxidase. The rate constant for compound I reduction by ascorbate is extremely fast (8.0 x 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 pKa value of 5.0 for a group affecting the active site reaction.
Related Concept Videos
01:19Enzyme Kinetics
Scientists typically study enzyme kinetics with a fixed amount of enzyme in the controlled environment of a test tube. When more reactant, or substrate, is...
01:19Protein Dynamics in Living Cells
Fluorescent recovery after photobleaching (FRAP) is a fluorescent-protein-based detection technique used to quantify protein movement rates within the cell. This method exposes a small portion of the cell to an intense laser beam. The laser beam causes permanent photobleaching of the fluorophore-tagged proteins in the exposed region. As the bleached...