Purification and properties of an iodide peroxidase from submaxillary gland of goat

Abstract

An iodinating enzyme has been identified and partially purified from the homogenate of goat submaxillary gland. The iodinating enzyme was purified 130-fold and found to be closely associated with iodide peroxidase activity in every step of purification. The finally purified preparation, although not homogeneous, exhibited both iodinase and peroxidase activities. The iodinase and the iodide peroxidase activities have comparable pH curves, hydrogen peroxide requirement and similar reactions towards some common reagents. Partial inactivation by pronase digestion also affects the two activities in a similar manner and fails to dissociate them. These observations led us to suggest that a single enzyme is responsible for the oxidation of I^- and incorporation of active iodine to the tyrosine moiety. The enzyme catalyses a production of 31.0 μmol triiodide ×min^-1× mg^-1 and can also catalyse effectively the oxidation of o-dianisidine which is stimulated 2000% in presence of KI. The enzyme also catalyses the iodination of thyroglobulin and albumin, other than free tyrosine, with the formation of iodotyrosines.