Studies on the invitro formation of monoiodotyrosine by soluble supernatant of pigeon thyroid gland.

Abstract

A soluble supernatant preparation of pigeon thyroid gland can catalyse the iodination of tyrosine to monoiodotyrosine in vitro. The enzyme needs a hydrogen peroxide generative system such as glucose and glucose oxidase or Cu2+ for its activity. The optimum concentration of Cu2+ was found to be 1·33 x 10−3 M. Direct and slow addition of hydrogen peroxide cannot be substituted for Cu2+.Antithyroid agents like thiourea and thiouracil are found to be more potent inhibitors of avian enzyme than of mammalian enzyme. Ascorbic acid inhibits the enzyme but stimulates remarkably when a dialysed enzyme is used instead of an undialysed one.