ENZYMES WHICH CATALYZE THE ORGANIC BINDING OF IODILS

Abstract

An iodide oxidizing enzyme system has been discovered in extracts of thyroid and certain salivary gland tissues which promotes the formation of elemental iodine. This anzymo system appears to function as a part of the previously reported tyrosine iodinase system which catalyzes the formation of monoiodo tyrosine, a precursor of thyroxine, from tyrosine. A mitochondrial enzyme system, which iodinates tyrosine residues in protein chains and which was previously reported to occur solely in the thyroid gland, has been detected in a number of extrathyroidal centers. Similarities in behaviour towards substrates and the co-existence of the mitochondrial arid tyrosine iodinasa systems in tissues may indicate that the systems uro basically the sama. rho tyrosine iodinuse system has been used to distinguish between two mechanisms developed to explain the anti-thyroid action of excess iodide ion.