Processing of preproGLP-1 to proGLP-1 Authored: May, B, 2009-05-18 21:31:59 EC Number: 3.4.21 Edited: May, B, 2009-09-09 Reactome Database ID Release 43400459 Reactome, http://www.reactome.org ReactomeREACT_23907 Reviewed: Bloom, SR, 2010-06-24 The GCG (Proglucagon) mRNA is translated by ribosomes at the outer surface of the rough endoplasmic reticulum. The nascent peptide enters the endoplasmic reticulum through the translocon complex and the signal peptide is cleaved by the signal peptidase.