Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 1 de 1
Filtrar
Mais filtros











Base de dados
Intervalo de ano de publicação
1.
FEBS J ; 273(24): 5574-88, 2006 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-17212776

RESUMO

A single membrane-bound aminopeptidase N (APN) occurs in the pea aphid (Acyrthosiphon pisum Harris) midgut, with a pH optimum of 7.0, pI of 8.1 and molecular mass of 130 kDa. This enzyme accounts for more than 15.6% of the total gut proteins. After being solubilized in detergent, APN was purified to homogeneity. The enzyme is a glycoprotein rich in mannose residues, which binds the entomotoxic lectins of the concanavalin family. The internal sequence of APN is homologous with a conservative domain in APNs, and degenerated primers of highly conserved APN motifs were used to screen a gut cDNA library. The complete sequence of APN has standard residues involved in zinc co-ordination and catalysis and a glycosyl-phosphatidylinositol anchor, as in APNs from Lepidoptera. APN has a broad specificity towards N-terminal amino acids, but does not hydrolyze acidic aminoacyl-peptides, thus resembling the mammalian enzyme (EC 3.4.11.2). The kcat/Km ratios for different di-, tri-, tetra-, and penta-peptides suggest a preference for tripeptides, and that subsites S1, S2' and S3' are pockets able to bind bulky aminoacyl residues. Bestatin and amastatin bound APN in a rapidly reversible mode, with Ki values of 1.8 microM and 0.6 microM, respectively. EDTA inactivates this APN (k(obs) 0.14 M(-1) x s(-1), reaction order of 0.44) at a rate that is reduced by competitive inhibitors. In addition to oligopeptide digestion, APN is proposed to be associated with amino-acid-absorption processes which, in contrast with aminopeptidase activity, may be hampered on lectin binding.


Assuntos
Aminopeptidases/isolamento & purificação , Aminopeptidases/metabolismo , Afídeos/enzimologia , Sistema Digestório/enzimologia , Lectinas de Ligação a Manose/metabolismo , Sequência de Aminoácidos , Aminopeptidases/genética , Animais , Afídeos/citologia , Sequência de Bases , Sítios de Ligação , Ligação Competitiva , DNA Complementar/biossíntese , DNA Complementar/genética , Cinética , Lepidópteros/enzimologia , Lectinas de Ligação a Manose/farmacologia , Dados de Sequência Molecular , Filogenia , Alinhamento de Sequência , Especificidade por Substrato
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA