抄録
Modification of basic amino acid residues of bovine liver catalase [EC 1. 11. 1. 6] with increasing concentrations of acrylonitrile or glyoxal caused inactivation of catalatic activity, enhancement of unspecific peroxidatic activity, and unfolding of apocatalase moiety corresponding to the concentration of modifying reagent. At lower concentrations of acrylonitrile (0-0.42M) the grade of inactivation was linearly correlated with the amount of lysine residues modified, but the modification of histidine and arginine residues was initiated by higher acrylonitrile concentrations. Higher concentration of acrylonitrile (0.98M) partly split catalase to completely inactive subunit (“1/4” fraction) which was separable from the “4/4” fraction by gel filtration. The decrease in catalatic activity by acrylonitrile from 100 to 62% (“4/4”) linearly correlated with the unfolding grade. The glyoxal-inactivation was accompanied by modification of arginine residues, and to lesser extents, lysine and histidine residues, and the inactivation parallelled with a small degree of unfolding. Higher concentrations of glyoxal, however, caused an abrupt increase in unfolding as well as complete inactivation. The spectroscopic changes characteristic to denaturation of catalase were observed with acrylonitrile- or glyoxal-inactivated catalase undergoing higher grades of modification of basic amino acid residues. A possible role of histidine residues is discussed in association with dissociation of catalase molecule (tetramer) by acrylonitrile.
