Isolation of a Parathyroid Polypeptide from Acetic Acid Extracts of Bovine Parathyroid Glands zx-

Thus far, three methods have been used for the extraction of the parathyroid hormone from bovine parathyroid glands (2-4). The first was that introduced by Collip in 1925 (2) in which hot dilute hydrochloric acid was the extracting agent. Further purification of such acid extracts has proven difficult, but recently the purification of parathyroid polypeptides from such extracts has been reported (5). These polypeptides (parathormone A) range in molecular weight from 3800 to 5200 and undoubtedly represent fragments of a larger nat.ive hormone (6). As early as 1955, Davies and Gordon (3) recognized the possibility that the difficulty encountered in purifying hydrochloric acid extracts might be due to partial acid hydrolysis of certain labile peptide bonds, and decided for this reason, to use hot 80% acetic acid as an extracting agent. Some further purification of such acetic acid extracts has been achieved by ultrafiltration (3) and zone electrophoresis (7). It is the purpose of this report to describe the isolation of an active polypeptide from acetic acid extracts of bovine parathyroid hormone. The data indicate that this polypeptide (parathormone 13) has a molecular weight of approximately 7000 and is composed of 62 amino acid residues. Furthermore, a comparison of the amino acid composition of this polypeptide with that of the pure polypeptide (M. W. 9450, 83 amino acid residues) obtained from phenol extracts of bovine glands (6) indicates that the present polypeptide (parathormone B) is undoubtedly a fragment of the larger phenol-extracted material (parathormone C). This is of interest in that it indicates that hydrolysis of certain labile peptide bonds occurs during the extraction of parathyroid hormone with hot 80°?0 acetic acid.