Abstract

New data concerning molecular structure, localization and functions of iodothyronine deiodinases in animal and human organisms are reviewed in the article. Mechanisms of 5- and 5'-deiodination of thyroid hormones by intracellular iodothyronine deiodinases are considered, the role of these enzymes in the processes of biologically active iodothyronine formation and thyroid hormone inactivation are shown. The data which suggest functioning iodothyronine-5'-deiodinases in the cells of haemopoietic and lymphopoietic systems, and connection between the rate of enzyme expression and cell differentiation level are adduced. Participation of thyroid hormones and other factors in the regulation of expression and functional activities of iodothyronine-5'-deiodinases in the cells is discussed. The important role of iodothyronine deiodinases in mechanisms of optimization of intracellular thyroid status in altered physiological state of organism, during ontogenesis and in pathological conditions is considered.