This is amino acid sequence of rat C-peptide-1. C-peptide binds specifically to cell surfaces, probably to a G protein-coupled surface receptor, with subsequent activation of Ca2+-dependent intracellular signaling pathways. It also stimulates Na+-K+-ATPase and endothelial nitric oxide synthase activities. Rat C-peptide was found to diminish glucose-stimulated insulin release in rats both in vivo and in vitro.
Pyroglutamyl (pGlu) peptides may spontaneously form when either Glutamine (Q) or Glutamic acid (E) is located at the sequence N-terminus. The conversion of Q or E to pGlu is a natural occurrence and in general it is believed that the hydrophobic γ-lactam ring of pGlu may play a role in peptide stability against gastrointestinal proteases. Pyroglutamyl peptides are therefore considered a normal subset of such peptides and are included as part of the peptide purity during HPLC analysis.