Structure and biosynthesis of avian pancreatic hormones

The amino acid sequences of four avian insulins have been determined, namely domestic fowl, turkey, duck and goose. Those of domestic fowl and turkey are identical but differ from that of the duck and goose at three positions (Fig. 7.2). There are also differences in the size of the C-peptide, which is 28 residues in the domestic fowl and 26 in the duck. Another feature that is evident from the proinsulin sequence (Fig. 7.2) is that the C-peptide is less conserved than the A- and B-peptides. tW C-peptide simply acts as a link between the A- and B-peptides to enable the disulphide bridges to form. Domestic fowl insulin is more potent than bovine insulin in ellidting changes in metabolism in the domestic fowl. This has been attributed to the six differences in the amino acid sequences of the two proteins. 

Domestic fowl insulin-like growth factor 

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