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Efficiency of thyroglobulin as a thyroid hormone-forming protein
Ist Teil von
Biochimica et biophysica acta, 1973-04, Vol.303 (2), p.338-347
Ort / Verlag
Netherlands: Elsevier B.V
Erscheinungsjahr
1973
Quelle
Elsevier Journal Backfiles on ScienceDirect (DFG Nationallizenzen)
Beschreibungen/Notizen
The [
127I]iodoamino acid composition of human thyroglobulin has been studied by chromatography after iodination
in vitro in different buffer systems. It has been compared to that of
in vitro iodinated human serum albumin and to that of
in vivo iodinated human thyroglobulin. Comparison of thyroglobulin iodinated
in vivo and
in vitro showed that, for iodine contents between 0.017 and 0.6%, the number of iodotyrosine residues per mole of protein was far higher in
in vitro iodinated thyroglobulin although the reverse was true for iodothyronines. Between 1 and 5 iodine atoms per mole of
in vivo iodinated thyroglobulin, an average value of 20% of total iodine was recovered in iodothyronines (thyroxine + triiodothyronine) and 40 to 50% for an iodine content of 20 to 25 atoms per mole.
In vitro iodination of human goitre thyroglobulin at alkaline pH or in 6 M guanidine resulted in the decrease or the suppression of iodothyronine formation although the number of tyrosine residues available for iodination increased.
In vitro iodination of human serum albumin did not result in the formation of significant amounts of iodothyronines even for a protein iodine content of about 4%. It is concluded that thyroglobulin is a very efficient thyroid hormone-forming protein and that the native conformation of the protein is necessary for optimal formation of thyroid hormone.