Characteristics of low molecular weight substances regulating plasma superoxide dismutase activity

Low molecular weight peptides which inhibit both plasma and red cell superoxide dismutase (SOD) activity have been isolated from human plasma. Several fractions of the substance were isolated chromatographically. The most active peptides have molecular weight about 1000 and 5000 D. The peptide lowering the SOD activity accelerates the hemoglobin oxidation reaction by NaNO2 and diminishes the laboratory animals' period of life in the process of intoxication by NaNO2. Another peptide was also isolated from human plasma and increased the SOD activity. The work is in progress on purification of this substance and investigation of its physical properties.