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. 1988 Dec 15;256(3):847–851. doi: 10.1042/bj2560847

Insulin proteinase liberates from glucagon a fragment known to have enhanced activity against Ca2+ + Mg2+-dependent ATPase.

K Rose 1, L A Savoy 1, A V Muir 1, J G Davies 1, R E Offord 1, G Turcatti 1
PMCID: PMC1135493  PMID: 2975945

Abstract

We find, contrary to previous reports, that substantial cleavage of glucagon by insulin proteinase occurs at only one region, namely the double-basic sequence -Arg17-Arg18-. Cleavage takes place almost exclusively between these two residues, liberating fragments glucagon-(1-17) and glucagon-(18-29). Others have shown that the fragment glucagon-(19-29) is 1000-fold more efficient compared with intact glucagon, at inhibiting the Ca2+-activated and Mg2+-dependent ATPase activity and the Ca2+ pump of liver plasma membranes. We show that this fragment is not liberated in detectable quantities by our insulin proteinase preparation. On the other hand, others have shown that glucagon-(18-29), though less active than glucagon-(19-29), was still 100-fold more active than glucagon itself in the above-mentioned system. Our observations represent the first demonstration of the release by insulin proteinase of a hormone fragment having enhanced activity, although it has yet to be shown that the activity of this fragment is important in vivo. Since the formation of glucagon-(19-29) from glucagon-(18-29) would involve merely removal of Arg18, a second enzyme might exist to provide the more active fragment.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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