Synthesis of a biologically active N-terminal tetratriacontapeptide of parathyroid hormone.

Determination of the amino acid sequence of bovine parathyroid hormone has led to the synthesis of a tetratriacontapeptide corresponding to the amino-terminal 1-34 residues of the native molecule. The specific biological effects of this synthetic peptide on bone and kidney are qualitatively identical to those of the native hormone in classical bioassays in vivo and in several systems in vitro. Potency of the synthetic peptide equals or exceeds that of a biologically active fragment of comparable size isolated from the native hormone; the synthetic and natural peptides show complete immunological cross-reactivity. Thus, essential requirements for the physiological actions of the peptide on both skeletal and renal tissue are contained within the 34 amino-terminal amino acids. The potency of the synthetic peptide, relative to that of the native (84-amino acid) polypeptide, is greater in vitro than in vivo; this suggests that the carboxyl terminal two-thirds of the native hormone may protect the circulating polypeptide from rapid metabolic degradation.