J. Michelot, J. Maurizis, C. Nicolas
May 17, 1978
Citations
0
Influential Citations
5
Citations
Quality indicators
Journal
Biochimica et Biophysica Acta
Abstract
Abstract It was previously shown that 3,5-diido- l -tyrosyl-3,5-diiodo- l -tyrosine, I 2 Tyr-I 2 Tyr, acts as a precursor in the in vitro synthesis of thyroid hormones, and a mechanism of syntheis was proposed. We investigated this pathway by incubations of I 2 Tyr-I 2 Tyr with microsomal solubilized thyroid proteins. I 2 Tyr-T 2 Tyr was doubly labeled: iodinated with 131 I on the ring and tritiated either on the alanine side-chain of the N- or C-terminal diidotyrosine. It is shown that only the C-terminal alanine participates in the synthesis, the N-terminal alanine being eliminated. The result proved that I 2 Tyr-I 2 Tyr acts as precursor through a mechanism which is different from the one involving I 2 Tyr. This mechanism consists of: Schiff base formation with pyridoxal; free radical formation and cyclization; peptide bond cleavage and removal of the pyridoxal · alanine complex.