Inactivation of heart dihydrolipoamide dehydrogenase by peroxidase-dependant oxidant systems

Incubation of heart dihydrolipoamide dehydrogenase (LADH) with pro-oxidant systems constitued by myeloperoxidase, H2O2 and an electron donor (a peroxi dase substrate) produced a time-dependent inactivation of LADH. Similar res ults were obtained with horseradish peroxidase and lactoperoxidase instead of myeloperoxidase. LADH inactivation is attributed to free radicals result ing from the oxidation of peroxidase substrates. 2,2'-azino-bis(3-ethylbenz othiazine-6-sulfonic acid), chloropromazine, trifluoperazine, catechol, Nor -dihydroguaiaretic acid, gossypol, guaiacol, quercetin and Paracetamol radi cals would produce LADH inactivation. Thiol compounds (GSH and N-acetilcyst eine), prevented LADH inactivation by the pro-oxidant systems.