Citation

Arnao MB, Acosta M, del Río JA, Varon R, García-Cánovas F. Biochim. Biophys. Acta 1990; 1041(1): 43-47.

Copyright

(Copyright © 1990, Elsevier Publishing)

DOI

10.1016/0167-4838(90)90120-5

PMID

2223846

Abstract

In the absence of reductant substrates, and with excess H2O2, peroxidase (donor: hydrogen-peroxide oxidoreductase, EC 1.11.1.7) shows the kinetic behaviour of a suicide inactivation, H2O2 being the suicide substrate. From the complex (compound I-H2O2), a competition is established between two catalytic pathways (the catalase pathway and the compound III-forming pathway), and the suicide inactivation pathway (formation of inactive enzyme). A kinetic analysis of this system allows us to obtain a value for the inactivation constant, ki = (3.92 +/- 0.06) x 10(-3) x s-1. Two partition ratios (r), defined as the number of turnovers given by one mol of enzyme before its inactivation, can be calculated: (a) one for the catalase pathway, rc = 449 +/- 47; (b) the other for the compound III-forming pathway, rCoIII = 2.00 +/- 0.07. Thus, the catalase activity of the enzyme and, also, the protective role of compound III against an H2O2-dependent peroxidase inactivation are both shown to be important.

Language: en

Keywords

Horseradish Peroxidase; Hydrogen Peroxide; Kinetics; Mathematics; Models, Theoretical; Protein Binding; Spectrophotometry