Chemical and biological properties of porcine secretin and secretin analogues modified in positions 3 and 4.
ABSTRACT The synthesis of secretin does not offer fundamental difficulties any longer. The problem of the stability of the hormone seems to be solved from a practical point of view. However, the mechanism of the inactivation of secretin in solution is not yet satisfactorily explained, alpha-beta Rearrangement of the Asp-Gly bond may play a role, but some observations indicate that inactivation is not a straight reaction. Like secretion [Ala-4] secretin shows beta-sympathomimetic activity. The availability of a suitable depot preparation permits physiological studies with secretin and its analogues after subcutaneous administration.
Article: New analogues of secretin.[Show abstract] [Hide abstract]
ABSTRACT: For the evaluation of structure/activity relationships, some porcine secretin analogues, modified in the N-terminus, have been synthesized by segment condensation in solution. The secretin activity of the analogues was defined as the volume of pancreatic juice secreted in rats and dogs. The exchange of the N-terminal pentapeptide for the N-terminal pentapeptide of human somatotropin releasing factor (h-SRF) resulted in a peptide ([1-Tyr,2,4-Di-Ala,5-Ile]secretin) with practically no SRF-activity (less than 1% SRF-activity up to 100 micrograms/kg in the rat), but surprisingly high secretin activity (almost 100% in the rat, but only 1150 CU/mg (27%) in the dog). [3-L-Cysteic acid]secretin showed 1750 CU/mg (39%) in the dog, but a less activity (23%) in the rat. [6-D-Phe]secretin and [5-D-allo-Thr]secretin are again strongly species specific. They exhibited an activity of less than 1% in the dog, but about 10-15% in the rat. The smallest secretin activity was observed with [1-Cys,6-Cys]secretin in the oxidized form. The activity in the rat with this analogue was only about 0.2%.Peptides 02/1986; 7 Suppl 1:61-7. DOI:10.1016/0196-9781(86)90165-8 · 2.61 Impact Factor
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ABSTRACT: A cloned synthetic DNA fragment coding for 27-desamidosecretin (DAS), which differs from natural porcine secretin by the lack of the amide group at the carboxyl-terminal valine residue, was fused to the β-galactosidase gene (lacZ) at the EcoRI site near the 3'-terminus of the gene. The fusion gene was efficiently expressed in Escherichia coli, yielding 1.15 × 106 fused-protein molecules per cell. After the treatment of the fused protein with cyanogen bromide, DAS was purified by a combination of ion-exchange column chromatography and reverse-phase high-performance liquid chromatography (HPLC). The structure of bacterial DAS was confirmed by tryptic mapping and amino acid composition analyses. The bacterial DAS was not amidated at its carboxyl-terminal valine residue. Nevertheless, it stimulated pancreatic secretion in rats as does authentic porcine secretin, indicating that the carboxyl-terminal amide is not essential to secretin activity.Gene 07/1984; 29(1-2-29):125-134. DOI:10.1016/0378-1119(84)90173-2 · 2.08 Impact Factor
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ABSTRACT: Membrane adenylate cyclase from rat heart was activated by the two gut peptides secretin and vasoactive intestinal peptide (VIP), glucagon, and the -adrenergic drug isoproterenol, in the presence of guanosine 5-triphosphate (GTP). With all the stimuli tested, the optimal magnesium concentration was 5 mM, i.e. in excess over the 0.5 mM ATP substrate concentration and 0.01 mM GTP used as cofactor. Under these conditions, half-maximal adenylate cyclase activation with glucagon, secretin, and VIP was achieved at concentrations of 0.5, 0.5 and 1.0 M, respectively. Data obtained with the secretin (7–27) fragment, a secretin antagonist, indicate that secretin and VIP acted on the same binding sites, which differed from glucagon binding sites. Structural requirements for secretin activation of cardiac adenylate cyclase were evaluated by comparing the potency and efficacy of parent peptides and synthetic analogs. The gastric inhibitory peptide GIP was inactive. When using 13 mono-or bi-substituted analogs, it appeared that amino acids in positions 1, 2, 3, 4 and 6 were of major importance while those in position 5 and 11 played a relatively minor role.Pflügers Archiv - European Journal of Physiology 12/1980; 389(1):21-27. DOI:10.1007/BF00587924 · 3.07 Impact Factor