L. Gebicka et Jl. Gebicki, MODIFICATION OF HORSERADISH-PEROXIDASE INDUCED BY HYDROXYL RADICALS -THE INFLUENCE OF OXYGEN, Biochimie, 78(1), 1996, pp. 62-65
Reactions of hydroxyl radicals with horseradish peroxidase (HRP) have
been studied by means of pulse radiolysis technique in the absence and
presence of oxygen. Hydroxyl radicals, produced in excess towards enz
yme, react exclusively with the protein part of HRP with the rate cons
tant k = 1.1 x 10(11) M(-1) s(-1). Activity loss induced by OH. is con
nected with such an enzyme modification that causes both the interfere
nce with substrate binding and partial blocking of the channel used by
peroxide. It is shown that in the presence of oxygen the loss of acti
vity is ca 10% higher, mainly due to restrictions in the formation of
compound I, ie ferryl [Fe(IV)=O] pi-radical cation.