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| Figure 3: The Posttranslational Processing of Proglucagon and GLP-1. In the pancreas, proglucagon (A) is cleaved to glucagon, GRPP, IP1 and MPGF by PC2, which comprise amino acids 33-61, 1-30 and 72-158 of proglucagon, respectively (B). In the intestinal L-cells proglucagon is processed by PC3 to GLP-1, GLP-2, IP2, oxyntomodulin and glicentin which are composed of amino acids 78-107, 126-158, 111-123 and 33-69 of proglucagon respectively (C). GLP-1 (7-37) and GLP-1 (7-36) amide are the active forms of GLP-1 in the body, both are quickly degraded by DPP-IV into inactive GLP-1 (9-37) and GLP-1 (9-36) amide, respectively, as indicated (D). The cleavage site is indicated by the arrow. |
