Iodotyrosine deiodinase

Iodothyronine deiodinase (not the enzyme that is the topic of this article) uses a selenocysteine active site for catalysis, is a member of the thioredoxin superfamily, and removes iodide only when the substrate is in a double-tyrosine form.

[10] By contrast, iodotyrosine deiodinase (the topic enzyme) does not require selenocysteine or cysteine for catalysis,[11] is part of the NADH oxidase/flavin reductase superfamily,[12][13] and removes iodide when the substrate is a single amino acid.

Thus, iodide levels must be regulated in order to keep thyroid hormones, and ultimately the organism's metabolic rate and overall health, in good status.

[20] Iodotyrosine deiodinase is located on the apical plasma membrane of the thyroid colloid, where mono- and diiodotyrosine are produced from this breakdown of thyroglobulin.

Without iodotyrosine deiodinase activity, the iodide would be excreted with the amino acid tyrosine and thyroid hormone biosynthesis would be reduced.

[14] The enzymatic activity of iodotyrosine deiodinase has also been known to exist in the tissues of the liver and kidneys as well;[21] however, the physiological significance of these findings is not yet clear.

Although further research must be done to determine details of this mechanism, recent evidence seems to suggest that iodotyrosine deiodinase acts through one electron transfer reactions.

[25] The resulting high blood and urine concentrations of iodotyrosine can be used as a measure for diagnosis, as the iodide is not removed from the tyrosine residues effectively.

[26] In some countries, newborn babies are tested for congenital hypothyroidism and treated immediately if the disease is detected, safely preventing the development of mental retardation.