Opossum intestine contains a glucagon-68

The distribution and molecular forms of glucagon-immunoreactivity (IR) were determined in the gastrointestinal mucosa of an opossum (Didelphis virginiana), a New World marsupial. The concentration in stomach fundus mucosa (0.18 nmol/g) was about the same as in the mucosa of terminal colon (0.17 nmol/g). There was an increasing gradient of glucagon-IR in mucosa from duodenum (0.02 nmol/g) to terminal ileum (0.53 nmol/g). Sephadex gel filtration analysis revealed that glucagon-IR in stomach fundus elutes in the region of glucagon-29 while virtually all of the intestinal glucagon elutes in the region of glicentin. Intestinal glucagon was purified and its sequence determined. Opossum glicentin is a 68 amino acid peptide compared to the 69 amino acid glicentins of several other mammalian species. The deletion is located around residues 24-25 from the N-terminus. In addition to the deletion, the N-terminus has 11 and 13 amino acid substitutions, respectively, compared to the structures of dog and pig glicentins. The C-terminus octapeptide differs from the dog and pig peptides in 3 sites. The mid-portion glucagon-29 is identical in structure to chicken glucagon with both differing from the usual mammalian peptide by a substitution of Ser for Asn at the penultimate C-terminal position.