OxyFile #239

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.