CHARACTERIZATION OF INSULIN, GLUCAGON, AND SOMATOSTATIN FROM THE RIVER LAMPREY, LAMPETRA-FLUVIATILIS

Insulin has been isolated from an extract of the pancreas of an Agnath an, the river lamprey Lampetra fluviatilis. The primary structure of t he peptide (A-chain: GIVEQ CCHRK CSIYD MENYC N; B-chain: SALTG AGGTH L CGSW LVEAL YVVCG DRGFF YTPSK T) is the same as that of insulin from th e sea lamprey Petromyzon marinus. In contrast, Lampetra glucagon (HAQG S FTSDY SKYLD SKQAK DFVIW LMNT), isolated from an extract of intestine , is structurally more similar to human glucagon (five amino acid subs titutions) than to Petromyzon glucagon (six substitutions). Similarly, the primary structure of somatostatin (AAAAP GAAGG AQLPL GNRER KAGCK NFFWK TFSSC), isolated from Lampetra pancreas, contains eight amino ac id substitutions and an additional residue compared with Petromyzon so matostatin. Somatostatin, isolated from Lampetra brain, has an identic al structure to mammalian somatostatin-14 (AGCKN FFWKT FTSC), indicati ve of the same tissue-specific expression of different somatostatin ge nes that was previously observed in Petromyzon. In contrast to the red uced binding affinity of other fish insulins, lamprey insulin was equi potent with porcine insulin in inhibiting the binding of [3-[I-125]iod otyrosine-A14] human insulin to the human insulin receptor. (C) 1995 A cademia Press, Inc.