Iodotyrosine deiodinase

Iodotyrosine deiodinase, also known as iodotyrosine dehalogenase 1, is a type of deiodinase enzyme that scavenges iodide by removing it from iodinated tyrosine residues in the thyroid gland. These iodinated tyrosines are produced during thyroid hormone biosynthesis. The iodide that is scavenged by iodotyrosine deiodinase is necessary to again synthesize the thyroid hormones. After synthesis, the thyroid hormones circulate through the body to regulate metabolic rate, protein expression, and body temperature. Iodotyrosine deiodinase is thus necessary to keep levels of both iodide and thyroid hormones in balance.

Dehalogenation in aerobic organisms is usually done through oxidation and hydrolysis; however, iodotyrosine deiodinase uses reductive dehalogenation. Iodotyrosine deiodinase and iodothyronine deiodinase have been determined as the only two known enzymes to catalyze reductive dehalogenation in mammals. Although these two enzymes perform similar functions, they are structurally and mechanistically different. 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. By contrast, iodotyrosine deiodinase (the topic enzyme) does not require selenocysteine or cysteine for catalysis, is part of the NADH oxidase/flavin reductase superfamily, and removes iodide when the substrate is a single amino acid. Research on iodotyrosine deiodinase has historically been variable and slow due to its lack of stability and arduous purification. Only recently has this enzyme been studied more deeply.