Effect of the phosphonic analogue of tyrosine on tyrosine iodination.

ABSTRACT

Depositing ofDL-1-amino-2-(p-hydroxyphenyl)-ethylphosphonic acid (Tyr-P) on the chicken embryo induced a dose dependent decrease of the iodine uptake by the embryonic thyroid. Tyr-P interfered on iodination of tyrosine when tested with hog thyroid peroxidase (TPO) and with bovine lactoperoxidase (LPO); the analogue was recognized by the two enzymes but its affinity for TPO and LPO was respectively 3 and 7 fold higher compared with that of the natural substrate, suggesting that Tyr-P may act as an iodine trap.