Synthetic analogues of residues 1-34 of human parathyroid hormone: influence of residue number 1 on biological potency in vitro.

A biologically active tetratriacontapeptide of human parathyroid hormone, hPTH (1-34), has been synthesized together with a series of structural analogues involving changes at the amino-terminal residue. Acetylation of the terminal amino group results in a marked reduction in the biological potency as measured in the in vitro rat renal adenylyl cyclase assay. Deletion of the terminal amino group results in a loss of biological activity. Substitution of the amino-terminal serine residue with glycine gives a lowered potency whereas substitution with alanine results in a 2-5-fold increase in biological activity in the in vitro assay. The results are compared with the findings previously reported for a series of amino-terminal analogues of the bovine PTH 1-34 peptide.