RESUMO
Screening of chromogenic peptide substrates have shown that FXIIa readily splits substrates of D-Pro-Phe-Arg-pNA (S-2302) and -Gly-Arg-pNA (e.g. S-2222) types. The latter type is preferred in a system where kallikrein is present. By using the substrate S-2222 a method for the determination of beta FXIIa inhibitors has been designed. Chromatography data show that C1-esterase inhibitor is the major inhibitor of beta FXIIa in plasma. Preliminary studies have also been performed on the assay of FXII in human plasma. The procedure to obtain a complete activation of FXII has still to be studied.
Assuntos
Fator XII/metabolismo , Dipeptídeos , Humanos , Calicreínas/sangue , Oligopeptídeos , Especificidade por SubstratoAssuntos
Coagulação Sanguínea , Fibrinólise , Peptídeo Hidrolases/metabolismo , Peptídeos/farmacologia , Animais , Bovinos , Compostos Cromogênicos , Fator IX/metabolismo , Fator IXa , Fator X/metabolismo , Fator XI/metabolismo , Fator XIa , Fator Xa , Fibrinolisina/metabolismo , Humanos , Calicreínas/metabolismo , Ativadores de Plasminogênio , Ratos , Trombina/metabolismoAssuntos
Fator X , Oligopeptídeos/síntese química , Animais , Bovinos , Fator X/análise , Cinética , Oligopeptídeos/análiseRESUMO
The hydrolysis of 35 tripeptidyl-p-nitroanilides was studied with human plasmin and the kinetic parameters were determined. The individual contribution of the various side chains to the kinetic parameters was calculated by regression analysis. Considering Km, substrates having Z-D-Ile-Phe-Lys as well as H-D-Ile-Phe-Lys sequences were found to be the best, while Bz-Ile-Leu-Lys and pGlu-Leu-Lys sequences are the best for kcat. The Km values of substrates protected at N-terminus are lower, their kcat values are higher than those of the unprotected ones with the same sequence.
Assuntos
Anilidas/metabolismo , Fibrinolisina/metabolismo , Sequência de Aminoácidos , Humanos , Cinética , Conformação Molecular , Análise de Regressão , Relação Estrutura-Atividade , Especificidade por SubstratoRESUMO
The kinetic constants, KM, kcat and kcat/KM of human leukocyte chymotrypsin (Cathepsin G, E.C.3.4.21.20.) were determined with 33 N-protected and 16 N-unprotected tripeptidyl-p-nitroanilide substrates. The individual contributions of the amino acid side chains of the substrates at P1-P4 subsites to the kinetic parameters were calculated by regression analysis. As far as KM is concerned, the highest contributions yielded the structure of an "optimum" substrate PhCO-Ala-Val-Tyr-pNA. The contribution values permitted us to characterize the S1-S4 binding segment in the enzyme's binding site, interacting with the P1-P4 moieties of the substrate. The enzyme prefers uniformly hydrophobic substituents at the S1-S4 sites. The S1 primary specificity subsite of the enzyme can bind Leu and 2-aminohexanoic acid as well, besides the aromatic amino acids Phe, Tyr, Trp. Data were compared with those obtained when studying pancreatic chymotrypsin with the same substrates.
Assuntos
Catepsinas/sangue , Leucócitos/enzimologia , Anilidas , Sítios de Ligação , Catepsina G , Humanos , Cinética , Nitrocompostos , Oligopeptídeos , Ligação Proteica , Serina Endopeptidases , Especificidade por SubstratoRESUMO
Chromogenic peptide substrates for serine proteases have been designed by using two approaches: (1) by using the natural substrate as a model and (2) by structure-activity correlations obtained through screening of a large number of tripeptides. Some recent examples, substrates for kallikreins and urokinase are given.
Assuntos
Endopeptidases , Calicreínas , Peptídeos/análise , Ativador de Plasminogênio Tipo Uroquinase , Aminoácidos , Calicreínas/sangue , Relação Estrutura-AtividadeRESUMO
The factor Xa-sensitive substrate BZ-Ile-Glu-Gly-Arg-p-nitroanilide has been made more sensitive by making ester and amide derivatives of the gamma-carboxyl group of the glutamyl residue. The morpholinyl and piperidyl amides react 2.5 times more rapidly with factor Xa.
Assuntos
Fator X , Oligopeptídeos , CinéticaRESUMO
The chromogenic substrate S-2251 (H-D-Val-Leu-Lys-pNA), a selective and sensitive substrate for plasmin activity, has made it possible to develop simple and reproducible methods for the determination of antiplasmin and plasminogen in human plasma. These methods have been optimized and studied in detail and found to be very specific for the respective factors.
Assuntos
Fibrinolisina , Plasminogênio , Fibrinolisina/antagonistas & inibidores , Fibrinolisina/normas , Humanos , Estreptoquinase/farmacologiaRESUMO
The kinetic behaviour of bovine pancreatic chymotrypsin was studied with 22 N-protected and 17 N-unprotected tripeptidyl-p-nitroanilide substrates. The contribution of the individual side chains to the kinetic parameters were calculated by regression analysis. At subsite P1 (notation of Schechter and Berger, 1967, Biochem. Biophys. Res. Commun. 27, 157) Tyr seems to be better than Phe and Trp, concerning kcat values. At P2 subsite the best KM values were obtained with Gly and Ser, whereas the hydrophobicity of P2 subsite appears to be necessary for efficient catalytic activity. At P3 mainly polar amino acids, both with D and L configuration, were tested. They improve the solubility of substrates in aqueous medium, as well as the kinetic parameters. Suc(OMe) and Suc protecting groups at P4 increase significantly the catalytic activity compared to the aromatic ones. The obtained data were compared to the known substrate binding site of bovine pancreatic chymotrypsin.