Contactless conductivity detection for screening myrosinase substrates by capillary electrophoresis. 2014

Reine Nehmé, and Hala Nehmé, and Grégory Roux, and Deimante Cerniauskaite, and Philippe Morin, and Patrick Rollin, and Arnaud Tatibouët
Institut de Chimie Organique et Analytique (ICOA), Université d'Orléans, CNRS FR 2708, UMR 7311, Orléans, France. Electronic address: reine.nehme@univ-orleans.fr.

Myrosinase is a unique enzyme that catalyzes the hydrolysis of glucosinolates (GLS) to isothiocyanate (ITC), glucose and sulfate. Isothiocyanates display a diversified very interesting biological activity. In this study, capillary electrophoresis (CE) was used for the first time for evaluating myrosinase kinetics (maximum velocity Vmax and Michaelis-Menten constant Km) and to assess the affinity of a variety of substrates toward this enzyme. The pre-capillary approach was chosen since it is very simple to conduct. For this, the enzymatic reaction was performed in a micro-vial. The reaction mixture volume was of only 100 μL and the incubation lasted only 5 min at 37±1°C. Short-end injection of few tens of nanoliters (~25 nL) of the reaction mixture was performed which decreased analysis time without using any electroosmotic modifier. The sulfate produced was detected and quantified with a contactless capacitively coupled conductivity detector (C(4)D) allowing the evaluation of myrosinase kinetics. This study shows, that capillary electrophoresis with contactless conductivity detection can be very useful for monitoring myrosinase activity. Comparing to the conventional spectrophotometric method (1982), the CE method developed here is simple, automated, economic, rapid (incubation for few minutes) and robust. Results compared very well with those reported in literature using the conventional method. Moreover, the affinity of a variety of natural and synthetic glucosinolates toward this enzyme has been assessed for the first time.

UI MeSH Term Description Entries
D007700 Kinetics The rate dynamics in chemical or physical systems.
D004553 Electric Conductivity The ability of a substrate to allow the passage of ELECTRONS. Electrical Conductivity,Conductivity, Electric,Conductivity, Electrical
D005961 Glucosinolates Substituted thioglucosides. They are found in rapeseed (Brassica campestris) products and related cruciferae. They are metabolized to a variety of toxic products which are most likely the cause of hepatocytic necrosis in animals and humans. Glucosinolate
D006026 Glycoside Hydrolases Any member of the class of enzymes that catalyze the cleavage of the glycosidic linkage of glycosides and the addition of water to the resulting molecules. Endoglycosidase,Exoglycosidase,Glycohydrolase,Glycosidase,Glycosidases,Glycoside Hydrolase,Endoglycosidases,Exoglycosidases,Glycohydrolases,Hydrolase, Glycoside,Hydrolases, Glycoside
D013053 Spectrophotometry The art or process of comparing photometrically the relative intensities of the light in different parts of the spectrum.
D013379 Substrate Specificity A characteristic feature of enzyme activity in relation to the kind of substrate on which the enzyme or catalytic molecule reacts. Specificities, Substrate,Specificity, Substrate,Substrate Specificities
D013431 Sulfates Inorganic salts of sulfuric acid. Sulfate,Sulfates, Inorganic,Inorganic Sulfates
D017879 Isothiocyanates Organic compounds with the general formula R-NCS.
D019075 Electrophoresis, Capillary A highly-sensitive (in the picomolar range, which is 10,000-fold more sensitive than conventional electrophoresis) and efficient technique that allows separation of PROTEINS; NUCLEIC ACIDS; and CARBOHYDRATES. (Segen, Dictionary of Modern Medicine, 1992) Capillary Zone Electrophoresis,Capillary Electrophoreses,Capillary Electrophoresis,Capillary Zone Electrophoreses,Electrophoreses, Capillary,Electrophoreses, Capillary Zone,Electrophoresis, Capillary Zone,Zone Electrophoreses, Capillary,Zone Electrophoresis, Capillary

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