Oxygen effect in the radiolysis of proteins. I. Lactate dehydrogenase.

Dose survival curves of lactate dehydrogenase irradiated under aerobic and anaerobic conditions show a sensitizing effect of oxygen for the inactivation of the enzyme. The oxygen effect in the radiolysis of lactate dehydrogenase was analysed by gel filtration and polyacrylamide gel electrophoresis. Under anaerobic conditions the main reaction is the aggregation caused by covalent non-covalent interaction of the protein molecules. Oxygen prevents both kinds of aggregation and instead it enhances peptide chain breakage. Protein fragments became obvious only after reduction of the irradiated proteins and could be separated by electrophoresis.