“ I- and H2O2, in addition to their function as primary substrates …, may act as alternative 'iodine acceptors' and therefore compete with tyrosine for the active iodinating agent, irrespective of whether this compound is an enzyme-associated … (E X I delta +) or an equivalent oxidized iodine species (IOH, IC1, I2).”
“Non-enzymatic (I2-mediated) and lactoperoxidase-catalyzed iodination of tyrosine are inhibited by excess iodide ( I- ) and/or hydrogen peroxide (H2O2).”