Flavianate, an amino acid precipitant, is a competitive inhibitor of trypsin at pH 3.0

Textile dyes bind to proteins leading to selective co-precipitation of a complex involving one protein molecule and more than one dye molecule of opposite charge in acid solutions, in a process of reversible denaturation that can be utilized for protein fractionation. In order to understand what occurs before the co-precipitation, a kinetic study using bovine ß-trypsin and sodium flavianate was carried out based on reaction progress curve techniques. The experiments were carried out using a-CBZ-L-Lys-p-nitrophenyl ester as substrate which was added to 50 mM sodium citrate buffer, pH 3.0, containing varying concentrations of ß-trypsin and dye. The reaction was recorded spectrophotometrically at 340 nm for 30 min, and the families of curves obtained were analyzed simultaneously by fitting integrated Michaelis-Menten equations. The dye used behaved as a competitive inhibitor of trypsin at pH 3.0, with Ki = 99 µM; kinetic parameters for the substrate hydrolysis were: Km = 32 µM, and kcat = 0.38/min. The competitive character of the inhibition suggests a specific binding of the first dye molecule to His-57, the only positively charged residue at the active site of the enzyme

Valor nutricional y contenido de factores antinutricionales de harinas precocidas de granos de Canavalia ensiformis / Nutritional value and antinutritional factors content of precooked flours prepared from Canavalia ensiformis

Precooked flours obtained five Canavalia ensiformis varieties were prepared by dehydration in double drums. On a dry matter basis, significant differences (P < 0.05) among varieties were detected for crude protein content (25 to 30 percent), starch (36 to 40 percent) and dietary fiber (13 to 15 percent). Hemagglutinins were eliminated as result of the high temperature (146 degrees C/4 min) employed during the drying process. Similar results were not obtained for trypsin inhibitors and canavanine considering that small amounts of these compounds remained in the precooked flours prepared from canavalia seeds. A 10 percent decrease in available lysine was observed. Biological assays yielded Protein Efficiency Ratio (PER) values of 0, 8-1 and Neat Proteic Relation (NPR) values of 2-3-2.6. True digestibility of protein values were improved from 87 to 90 percent. All cultivars had similar starch digestive utilization coefficient (96 percent) and starch fraction (4 percent) resistant to enzymatic hydrolysis in the rat digestive tract

Efectos de la fibra dietética sobre la digestibilidad de las proteínas y de la energía en ratas / Effect of the dietary fiber on protein and energy digestibilities rats

Se realizó un balance nitrogenado y de energía en ratas para determinar la influencia del nivel de fibra dietética sobre la digestibilidad de las proteínas y de la energía de 25 productos vegetales. Se tomó en consideración la presencia de inhibidores de tripsina, lectinas y polifenoles en algunos de estos productos. Cinco muestras se ensayaron crudas y calentadas. Se encontró una relación inversa significativa entre el nivel de fibra dietética y la digestibilidad de las proteínas y de la energía. La presencia de inhibidores de tripsina, lectinas y polifenoles y el proceso de calentamiento no pareció ejercer ninguna influencia. La fibra dietética fue el factor más importante asociado con la digestibilidad de las proteínas y de la energía en estas muestras

Interaction of bovine alpha2 macroglobulin with proteinases

Alpha2, Macroglobulina, uma proteína inibidora de proteases, foi isolada do plasma bovino. O processo de purificaçäo foi monitorado por imunodifusäo e imunoeletroforese cruzada com soro anti alpha2M-humana. Para as determinaçöes quantitativas foi preparado um soro anti alpha2M bovino. A preparaçäo mais pura de alpha2M foi obtida por cromatografia de afinidade e usada como padräo primário na imunodifusäo radial de Mancini. Preparaçöes de alpha2M foram usadas em testes de ligaçäo com tripsina e plasmina (tituladas com NPGB). Nos testes de ligaçäo 50 por cento de plasmina e 35 por cento de tripsina foram "protegidas" pela alpha2M. Näo foi possível determinar se houve incidência na ligaçäo ou se a perda de atividade ocorreu por alteraçöes na afinidade do complexo alpha2M-protease, em relaçäo aos substratos usados

Purification and preliminary characterization of Torresea cearensis trypsin inhibitor

An inhibitor against serine proteinases was purified from Torresea cearensis by affinity chromatography on trypsin-Sepharose. The protein is a single polypeptide of molecular weight 13,600 after reduction and has a high content of cysteine residues. Both trypsin (Ki = 0.34 nM) and chymotrypsin (Ki = 0.15 micronM) are inhibited by Torresea cearensis inhibitor. Blood clotting factor XII is also inhibited (Ki = 24 micronM), but not plasma kallikrein, tissue kallikrein or thrombin. The stoichiometry of the inhibitorproteinase complex with trypsin is 1:1

The complete amino acids sequence of the Vigna unguiculata (L.) Walp. seed trypsin and chymotrypsin inhibitor

Foi determinado em nosso Laboratório a seqüência completa de aminoácidos de um inhbidor de tripsina e quimotripsina, "double-headed", denominado abreviadamente BTCI, purificado de feijäo caupi Vigna unguiculata (L.) Walp.cv."Seridó". Os peptídeos trípticos e quimiotrípticos foram seqüenciados pelos métodos manuais de Edman-Gray, de Edman-Chang (N-terminais) e de carboxypeptidases (C-terminais). É a seguinte a seqüência de aminoácidos do BTCI: Ser Gly-His-Glx-Asx-Ser-Thr-Asx-Glx-Ala-Ser-Glx-Ser-Ser-Lys-Pro-Cys-Cys-Arg-Glx-Cys-Ala-Cys-Thr-Lys-Ser-Ile-Pro-Pro-Glx-Cys-Arg-Cys-Ser-Asx-Val-Arg-Leu-Asn-Ser Cys-His-Ser-Ala-Cys-Lys-Ser-Cys-Thr=Phe-Ser-Ile-Pro-Ala-Glx-Xys-Phe-Cys-Gly=Asx-Ile-Asx-Asx-Phe-Cys=Tyr-Lys-Pro-Cys-Lys-Ser-Ser-His-Ser-Asx-Asx-Asx-Asx0Trp-Asn. BTCI apresenta alto grau de homologia como vários outros inibidores da família Bowman-Birk