Studies on the solid phase synthesis of the c-terminal dodecapeptide of basic pancreatic trypsin inhibitor and the c-terminal pentapeptide amide of avian pancreatic hormone III

The synthesis of a peptide corresponding to the C-terminal dodecapeptide of BPTI, and a pentapeptide amide equivalent to the C-terminal fragment (36-32) of PH-III, was undertaken using the solid phase method. There were three attempts towards the synthesis of each peptide. All syntheses proceeded in satisfactory yields; however, due to great losses experienced during the cleavage of the product from the resin, and the purification procedures, we were able to isolate only small amounts of product. The products isolated from the syntheses of the two peptides, have behaved in all occasions as it would be expected from the corresponding fragments of the biological molecules and were considered identical to them. The synthesized molecule corresponding to the C-terminal dodecapeptide, was used in association with Fragment "A" (1-52) obtained from reduced CNBr cleaved BPTI. The ability of this peptide to serve as a nucleation site for the proper folding of Fragment "A", was tested by the extent of trypsin inhibition. The results obtained were negative. The product obtained from the synthesis of the C-terminal pentapeptide amide, was tested for biological activity by injecting it into a chicken and recording any changes in the gastric flow volume. This peptide has been proposed to be the active site of the hormone. There were no data obtained from the biological tests supporting such a suggestion. There was, however, a definite suppression of the gastric flow excretion observed, indicating the possible interaction of the synthetic product with the hormone receptor.