Enzymes named  for this element are classified as inner ring donors or outer ring donors.
A transporter for this element is under-produced in Allan-Herndon-Dudley syndrome. Enzymes named  for this element are classified as inner ring donors or outer ring donors. An acetamide or acetate bound to this element inhibits cysteine peptidases and was used to determine the mechanism of GAPDH. Peroxidases named for this element have a crucial selenocysteine residue and are labelled D1 through D3.  Pendrin transports this element into the follicular lumen. Incorporation of this element, or (*) "organification," is impaired at high concentrations of it in the Wolff-Chaikoff effect. A cell viability stain couples FDA to the propidium salt of this element. Removing an atom of this element from a tyrosine residue in T4 produces T3. It forms visible complexes with crystal violet. For 10 points, name this element found in thyroxine, which you should eat if you don't want a goiter.
A transporter for this element is under-produced in Allan-Herndon-Dudley syndrome.
iodine [or I] 