Studies on polypeptides. V. Improved synthesis of human proinsulin C-peptide and its benzyloxycarbonyl derivative. Circular dichroism and immunological studies of human C-peptide.
An improved synthesis of human C-peptide is described. Five fragments: 33-39, 40-46, 47-49, 50-54 and 55-63 were used in the total synthesis. In the fully protected C-peptide the N-terminal alpha-amino function was blocked by a benzyloxycarbonyl group and the carboxyl and serine hydroxyl functions were blocked by t-butyl protection.  The latter protecting groups were removed by trifluoroacetic acid to obtain N-alpha-benzyloxycarbonyl human C-peptide which, on catalytic hydrogenation, yielded human C-peptide. The immunoreactivity of the prepared human C-peptide was tested and found to deviate slightly from the human C-peptide synthesized earlier by another route. When tested in the immunoassay, human pancreatic extracts containing natural C-peptide (or fragments thereof) showed dilution patterns identical to that of the new synthetic C-peptide but different from that of the previously synthesized batch of C-peptide. The possible explantation for the observed differences in the immunoreactivity is discussed.
D001593:Benzyl Compounds; D002942:Circular Dichroism; D006801:Humans; D009904:Optical Rotation; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000276:immunology; D011384:Proinsulin / Q000138:chemical synthesis* / Q000276:immunology; D011487:Protein Conformation; D013056:Spectrophotometry, Ultraviolet
D001593:Benzyl Compounds; D010446:Peptide Fragments; D011384:Proinsulin