Purificação e caracterização da insulina e de peptideos derivados do proglucagon e prossomatostatina isoladaos do, peixe frugivoro, pacu Piaractus mesopotamicus Holmberg, 1887 (Teleostei, Characidae Serrasalminae)

AUTOR(ES)
DATA DE PUBLICAÇÃO

1998

RESUMO

The fruit-eating teleost fish, the pacu Piaractus mesopotamicus Holmberg, 1887 (Characiformes, Characidae, Serrasalminae), similarly to tambaqui Colossoma macropomum, is classified with the carp and the catfish in the superorder Ostariophysi. The pacu and tambaqui have the pancreatic tissue exibiting both principal islet and small Brockmann bodies (Bbs). The pacu Bbs were analyzed histologically and shown to contain four kinds of endocrine cells (A. B, C, O) found in mammalian islets of Langerhans. Hormonal polypeptide in an extract of pacu Brockmann bodies were purified to homogeneity in high yeld by reversed phase HPLC and their primary structures determined by automated Edman degradation. The primary structure of pacu insulin was established as ? A chain: GIVEQCCHKPCSIFDLQNYCN, B-chain: NAGAPQHLCGSHLVDALYLVCGPSGFFYNPK. Pacu and tambaqui insulin are identical, they contain only two substitutions (Glu _ Asp at A15 and Thr _ Ser at B24) compared with carp insulin. The B-chains of both insulins contain a dipeptide extension in the N terminus and a deletion of the C terminal residue compared with human insulin. The pacu pancreas also synthesizes glucagon and GLP-1. The primary structure of pacu glucagon was established as: HSEGTFSNDYSKYLETQRAQDFVQWLMNS. Pacu glucagon differs from human glucagon by 7 amino acids and from catfish glucagon by a single substitution at position 17(Arg _ Gln). A Gln resídue at this position has not been observed previously in any teleostean or mammalían glucagon. The primary structure of pacu glucagon-Iíke peptide (GLP) was established as: ADGTYTSDVSAYLQDQAAKDFITWLKSGQPKQE. Pacu GLP contains 34 amino acid residues and differs from catfish GLP only at positions 12 (Ser - Ala) and 33 (pro - Gln). In common with other teleost species, the pacu expresses two somatostatin genes. Somatostatin-14, derived from preprosomatostatin-I (PSS-I), is identical to mammalían and catfish somatostatin-14. A fragment of prosomatostatin-22 showed 67% sequence identity with residues (1-58) of catfish preprosomatostatin-II (PSS-II). A comparison of the primary structures of the islets hormones suggest that amino acid sequences may have been more conserved within the Ostariophysi than in other groups of the taxon Euteleostei, that have been studied. Isolation of these hormones will now permit an investigation of their effect on lipide and carbohydrate metabolism in the serrasalminae fishes, pacu and tambaqui

ASSUNTO(S)

hormonios pacu (peixe) pancreas insulina

ACESSO AO ARTIGO

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