Aj. Grant et al., ENHANCED ENZYMATIC DEGRADATION OF RADICAL DAMAGED MITOCHONDRIAL-MEMBRANE COMPONENTS, Free radical research communications, 19(2), 1993, pp. 125-134
The location of a protein (soluble or membrane-bound) influences the e
xtent of oxidative damage caused by free radicals. It has been establi
shed that after radical attack, soluble proteins can become more susce
ptible to hydrolysis by individual proteinases than native proteins.1-
4 We have now examined the hydrolytic susceptibility following radical
attack of a protein that is located within a membrane environment, mi
tochondrial monoamine oxidase (MAO). After exposure to oxygen radicals
generated by gamma irradiation, hydrolysis of sub-mitochondrial parti
cles (SMP) containing MAO was increased in three respects. First, the
generation of small fragments of MAO by the proteinases elastase and t
rypsin, was enhanced. Second, the generation by these enzymes and by p
hospholipase A2 of non-sedimentable membrane fragments containing MAO
was also increased. Third, autolysis of SMP was enhanced. Hence, prote
ins located within membranes may become more susceptible to enzymatic
degradation following oxidative damage.