Characterization of insulin and atypically processed proglucagon-derived peptides from the Surinam toad Pipa pipa (Anura:Pipidae)

Insights into the evolution of proglucagon‐derived peptides and receptors in fish and amphibians

“…Like Agnathans and Osteichthyes, amphibians present yet another unique case of multiple proglucagon sequences. More specifically, proglucagon transcripts from the African clawed frog ( Xenopus laevis ), 37 Northern leopard frog ( Rana pipiens ), 38 tiger frog ( Rana tigrina rugulosa ), 39 and cane toad ( Bufo marinus ) 40 are found to encode up to three multiple in‐series GLP‐1s. Although phylogenetic analysis reveals the origin of these GLP‐1s to be traced back to a common frog ancestor (∼150 mya) prior to the initial divergence and are likely triplication products of the GLP‐1 exon early in the frog lineage, 41 the scarcity in known sequences complicates understanding of their evolution.…”

Using Evolutionary Information and Ancestral Sequences to Understand the Sequence–Function Relationship in GLP-1 Agonists

“…Tetrapod GLP-1 sequences were collected from databases and the literature; Agkistrodon piscivorus (GI:45272441), Amphiuma tridactylum (three-toed salamander), 56 Bufo marinus (giant toad), 21 Ceratophrys ornata (ornate horned frog), 57 Cynops pyrrhogaster (Japanese firebelly newt), 32 Gallus gallus (common chiken), 58 Hoplobatrachus rugulosus (Taiwanese frog), 23 Heloderma Suspectum (Gila monster), 24 Homo sapiens (human), 59 Pyxicephalus adspersus (African bull frog), 60 Pipa pipa (suriname toad), 61 Rana catesbeiana (bull frog), 62 Rana pipiens (northern leopard frog), 22 Xenopus leavis (African clawed frog), 32 Xenopus tropicalis (western clawed frog) (GI:55742076), and H. suspectum exendin-4. 25 Cleavage positions were in most cases determined from sequencing of the peptide itself; otherwise they were transferred from the closest homolog.…”

Comparative peptidomics of the endocrine pancreas: islet hormones from the clawed frog Xenopus laevis and the red-bellied newt Cynops pyrrhogaster

“…The present study has shown that preproglucagons from gene 1 and 2 are not processed to glucagon-29, the primary gene product in the pancreata of mammals, but to a C-terminally extended component that corresponds to mammalian glucagon-37 (oxyntomodulin) (Tager & Steiner 1973). The concentrations of C-terminally extended forms of glucagon are higher than the concentrations of glucagon-29 in the pancreata of several species of anurans that have been examined (Rana catesbeiana (Pollock et al 1988), Bufo marinus (Conlon et al 1998a), Ceratophrys ornata (White et al 1999) and Pipa pipa (Matutte & Conlon 2000)). As shown in Fig.…”