The toxic effects of oxygen on brain metabolism and on tissue enzymes

Abstract

Of the enzymes known or considered to be O2-sensitive, the dehydrogenase component of succinic oxidase is inhibited irreversibly by high O2 tensions. Cytochrome oxidase is affected after prolonged exposure. Only a minor part of the poisoning is due to the accumulation of oxaloacetate. Malonate (10-3 M) or Mn ions (2.5 X 10-4 M) protect dehydrogenase against poisoning by O2. Lactic and malic dehydrogenase from animal tissues were resistant to O2 inactivation. Flavoproteins, catalase and yeast hexokinase were also resistant. Triosephosphate dehydrogenase, cholineoxidase and phosphoglucomutase are poisoned by O2.