Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1234237 | Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy | 2010 | 5 Pages |
Abstract
Binding of nitric oxide to horseradish peroxidase (HRP) has been investigated by absorption spectrometry in 0.2 M anaerobic phosphate buffer solution (pH 7.4). Based on this binding equilibrium, a model equation for evaluating the binding constant of nitric oxide to HRP is developed and the binding constant is calculated to be (1.55 ± 0.06) Ã 104 Mâ1, indicating that HRP can form a stable complex with nitric oxide. The type of inhibition by nitric oxide is validated on the basis of studying initial reaction rates of HRP-catalyzed oxidation of guaiacol in the presence of hydrogen peroxide and nitric oxide. The inhibition mechanism is found to follow an apparent non-competitive inhibition by Lineweaver-Burk method. Based on this kinetic mechanism, the binding constant is also calculated to be (5.22 ± 0.06) Ã 104 Mâ1. The values of the binding constant determined by the two methods are almost identical. The non-competitive inhibition model is also applicable to studying the effect of nitric oxide on other metalloenzymes, which catalyze the two-substrate reaction with the “ping-pong” mechanism.
Keywords
Related Topics
Physical Sciences and Engineering
Chemistry
Analytical Chemistry
Authors
Li Qiang, Shuhua Zhu, Hongmei Ma, Jie Zhou,