Iodinated derivatives of the hormone avian pancreatic polypeptide.
Reaction of avian pancreatic polypeptide with an iodine monochloride reagent at both pH 4 and pH 7.5 results in the differential modification of the four tyrosine residues in this peptide hormone. A total of 19 distinct iodinated derivatives were isolated by reverse-phase high-performance liquid chromatography, and their sites of iodination were characterized by both tryptic mapping and leucine aminopeptidase techniques coupled with HPLC. The pH 4 reaction produced 16 derivatives which, overall, represented substantial iodination at each tyrosine residue, whereas the pH 7.5 reaction was more directed, producing only 7 derivatives. Iodination at the C-terminal tyrosineamide 36 predominated at both pH values, and diiodo-Tyr 36 was found in the majority of the pH 7.5 derivatives. The relative of the four tyrosine residues with ICl were as follows: at pH 7.5, Tyr 36 much greater than Tyr 21 much greater than Tyr 27 greater than Tyr 7; at pH 4, Tyr 36 greater than Tyr 27 greater than Tyr 7 greater than Tyr 21.
Taylor
T C
TC
Medical Research Service, Veterans Administration, Medical Center, Kansas City, Missouri 64128.
Kimmel
J R
JR
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D001717:Birds; D002851:Chromatography, High Pressure Liquid; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007455:Iodine / Q000032:analysis*; D010191:Pancreatic Polypeptide / Q000032:analysis*; D014357:Trypsin / Q000494:pharmacology; D014422:Turkeys; D014443:Tyrosine / Q000032:analysis
D014443:Tyrosine; C009725:pancreatic polypeptide, avian; D010191:Pancreatic Polypeptide; D007455:Iodine; D014357:Trypsin