Participation of thyroid D-aspartate oxidase in iodide oxidation and incorporation into thyroid proteins

It was found that the H2O2 generating system containing D-aspartate oxidase isolated from the thyroid gland and D-aspartate, takes part in oxidation of iodides. The molecular I2 formed under experimental conditions is subsequently incorporated into thyroid proteins. Thiosemicarbazide, thiourea, methylthiouracyl, sulphathiazole, thiocyanate and azides were found to have an inhibiting effect on iodide oxidation. Methimazole inhibits both the oxidation of iodide and incorporation of 131I into protein. The iodide incorporation was inhibited by catalase. The findings of these investigations suggest an indirect participation of D-aspartate oxidase in the synthesis of the thyroid hormone by supplying the essential substrate for the iodide oxidation, H2O2.