Tyrosine biological iodination

For iodination, proteins and peptides must have tyrosine, histidine, or primary amino groups (Figure 2.1). In addition, the biological activity must survive the iodination procedure. Tyrosine residues are often iodined with chloramine T. Chloramine T in watery solution slowly... 

Several examples of the applications of polarography in these fields have been already mentioned in Chapters VI and VII, viz. determinations of benzene, toluene, naphthalene and phenols in the atmosphere, breath, blood or urine, of amino acids (with particular interest to tyrosine, tryptophane, phenylalanine, histidine and histamine), of ketoacids, ketosteroids, carbon disulphide in air and blood, ethanol, acetoin, sugars and morphine in blood, of lactic acid, mandelic acid in bile and urine, adrenaline and thyroxine in iodinated proteins and last, but not least, of thiol compounds, both soluble and bound in biological materials. A few further examples will be given here. 

Furthermore the critical level of substitution cannot be only a consequence of the extent of the substitution on the single molecule, but it must correspond to the attainment of a critical intramolecular distribution of the substituent. In the case of iodination, evidence has been obtained (6) that the formation of di-iodinated tyrosine groups on the A chain represents the critical change at which the hormone loses its biological activity and one of the -S-S- bonds becomes unreactive. 

The polyandrocarpamides combine a derivative of phe-nylethylamine with an indole nucleus, which may be halogenated. Thus, polyandrocarpamide B is one of the rare iodinated derivatives isolated from an ascidian (Lindquist and Fenical, 1990). Polyandrocarpamines A and B are also derived from tyrosine and have a 2-amino-imidazolone. No particular biological property has been mentioned for these four derivatives. 

---