Isolation and structure of lamprey (Petromyzon marinus) insulin

Insulin has been purified to homogeneity from the caudal and cranial pancreas of the adult sea lamprey (Petromyzon marinus). The final yield was 18.6 nmol/g (127.8 micrograms/g). The structures of both A- and B-chains have been determined using amino acid analyses, gas-phase sequence analyses, and proteolytic mapping by fast atom bombardment-mass spectrometry. The sequence of the A-chain was found to be GIVEQCCHRKCSIYDMENYCN. The sequence of the B-chain, extended at the amino terminus, was determined to be SALT-GAGGTHLCGSHLVEALYVVCGDRGFFYTPSKT. Lamprey insulin retains the common features of vertebrate insulins. Sea lamprey insulin has no more homology to hagfish (Myxine glutinosa) insulin than it has to the teleost fish or to mammalian insulins.