Enzymic Iodination of Milk Proteins

Abstract

RECENTLY, Pitney and Russell Fraser¹ have reported studies in which they utilized, as a model system for antithyroid drug evaluation, a procedure based on that of Keston² for the enzymic iodination of milk proteins. This has prompted us to outline some of our observations with a similar system using purified milk enzymes and proteins. Native casein in a finely suspensible form was obtained from separated milk by differential high-speed centrifugation at 0°³. It was washed with water and freeze-dried from an aqueous dispersion. β-Lactoglobulin was prepared essentially according to Palmer⁴. In order to obtain lactoperoxidase (of about 40 per cent purity as judged by absorption data) the fraction of milk separating at 50–70 per cent saturation with ammonium sulphate was treated by an unpublished procedure developed by Dr. D. Morell, who also kindly provided a purified specimen of xanthine oxidase⁵.