Flavianate, an amino acid precipitant, is a competitive inhibitor of trypsin at pH 3.0
Braz. j. med. biol. res
;
31(9): 1105-11, sept. 1998.
Article
in English
| LILACS
| ID: lil-222956
RESUMO
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 FACE="Symbol">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
Full text:
Available
Index:
LILACS (Americas)
Main subject:
Proteins
/
Trypsin Inhibitors
/
Coloring Agents
/
Amino Acids
Language:
English
Journal:
Braz. j. med. biol. res
Journal subject:
Biology
/
Medicine
Year:
1998
Type:
Article
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