Amino acid modifications in canine, equine and porcine pituitary growth hormones, identified by peptide-mass mapping

Modified amino acid residues in porcine, canine and equine growth hormones purified from pituitary glands were characterised by tryptic mapping and hi gh-performance liquid chromatography with on-line coupled electrospray ioni sation mass spectrometry (HPLC-ESI-MS) detection. Hormones from all three s pecies showed the same changes. Conversion of Asp(128) to iso-Asp(128) was a component of native hormones, while deamidation of Asn(12) and Asn(98) to Asp and iso-Asp, Asp oxidation of Met(4), and cyclisation to the pyrogluta myl derivative of Gln(139), probably occurred in vitro, during isolation, s torage or hydrolysis. Porcine and canine hormones had indistinguishable pro tein fingerprints, confirming the assumption, based on their cDNA sequences , that their mature primary structures are identical. (C) 2001 Elsevier Sci ence B.V. All rights reserved.