Inactivation of an animal and a fungal catalase by hydrogen
peroxide.
Author: DeLuca DC; Dennis R; Smith WG
Source: Arch Biochem Biophys 1995 Jun 20; 320(1):129-34
Abstract:
We have quantitatively compared the rates of peroxide-dependent
inactivation of bovine liver catalase and Aspergillus niger
catalase as class representatives of catalases that contain
tightly bound NADPH and those that do not. Inactivation
of these catalases in the presence of ethanol has also
been quantitated in an effort to assess the importance
of compound II, an inactive form of bovine liver catalase,
in the inactivation reaction. The values of k2, the second-order
rate constant for inactivation calculated for the bovine
enzyme, in the absence and presence of ethanol, respectively,
were 8.9 +/- 0.26 and 8.5 +/- 0.27 M-1 min-1. In contrast,
the values for the A. niger enzyme were 0.51 +/- 0.069
and 10.5 +/- 0.32 M-1 min-1. The A. niger enzyme is more
stable toward hydrogen peroxide-induced inactivation than
the liver enzyme. The A. niger enzyme is markedly destabilized
by 20 mM ethanol, whereas the inactivation of the liver
enzyme is unaffected by ethanol. Reaction of bovine liver
catalase with ethyl hydroperoxide produced the characteristic
absorption spectrum of compound I and in the absence of
ethanol the spectrum associated with compound II. In contrast,
the fungal enzyme developed compound I spectrum but spectral
changes that might be ascribed to compound II were barely
detected in the Soret region. Spectral changes for A. niger
catalase in the visible region were modified by the presence
of ethanol but could not be clearly correlated with the
bovine catalase compound II spectra either in the presence
or absence of ethanol. The stability of the fungal and
bovine catalases in the presence of hydrogen peroxide is
quantitatively documented. The enzymes are also shown to
be different in their response to ethanol and in the formation
of compound II-like species with ethyl hydroperoxide. It
appears unlikely that compound II is an intermediate in
the hydrogen peroxide-mediated inactivation reaction of
either catalase under catalatic assay conditions.
Copyright © 2021 oxygentherapyexperts. All rights reserved.