Ascorbate oxidase and its possible involvement in cancer.

The electron spin resonance (ESR) spectrum of erythrocytes of a health male volunteer exhibited 2 min after intravenous administration of 1g of ascorbic acid a considerable increase in spin concentration and an new signal at about g-2.005 which we previously had found to correlate to the semidehydroascorbate (SDA) radical and which is not identical with the O2 radical. Moreover, the vitamin C concentration in erythrocytes and plasma was considerably higher than in comparable samples of other volunteers treated identically. In the latter cases, the ESR spectrum of the erythrocytes was not modified at all. These findings suggest that there must be a substance which reacts with ascorbic acid specifically. It can be assumed that the enzyme ascorbate oxidase plays this decisive role in the ascorbic acid metabolism. For this reason, different amounts of ascorbate oxidase have been added to healthy erythrocytes treated in vitro with ascorbic acid and to tissue samples of lung cancer. As expected, the vitamin C effect as expressed by the appearance of the SDA signal and the increase in spin concentrations could be reversed. It is suggested, therefore, that in special types of cancer, such as acute lymphatic leukemia and lung cancer, the concentration of ascorbate oxidase or of an enzyme acting like it is, primarily, diminished, while in other types it might be enlarged.