Application of Electrophoretically Mediated Microanalysis for Study of Ezymes
| Authors | |
|---|---|
| Year of publication | 2004 |
| Type | Article in Proceedings |
| Conference | Proceeding of 17th International Symposium on Microscale Separations and Capillary Electrophoresis |
| MU Faculty or unit | |
| Citation | |
| Field | Biochemistry |
| Keywords | capillary electrophoresis; microscale separations |
| Description | Enzymes are biological catalysts that play an important role in biochemical reactions necessary for normal growth, maturation and reproduction through the whole living world. They catalyze virtually all chemical reactions in living systems and the assay of enzyme activity is probably one of the most frequently encountered procedures in biochemistry and molecular biology. Due to their low concentrations in samples containing a large amount of other proteins, direct measurements of enzymes by mass are impossible. However, enzymes can be measured more easily by their catalytic activities, which are the most relevant properties of enzymes in the biochemical context. The enzyme assay is important procedure in elucidation of enzyme properties and function. Determination of kinetic parameters is usually undertaken to characterize an enzyme, to provide a quantitative evaluation of substrate specificity and to study kinetic mechanisms. Capillary electrophoretic systems have been successfully applied for in-line enzyme-catalyzed reaction by a methodology known as Electrophoretically Mediated MicroAnalysis (EMMA), firstly described by Bao and Regnier. In this method, substrate(s) and enzyme are introduced into the capillary as a distinct plugs, the first analyte injected being the one with the lower electrophoretic mobility. Upon the application of an electric field the two zones interpenetrate due to differences in their electrophoretic mobilities. Enzymatic reaction takes place and the resultant reaction product(s) and the unreacted substrate(s) are electrophoretically transported towards the detector, where they are individually detected. This approach was applied in the complex study of rhodanese, important enzyme catalyzing detoxication of cyanide to less toxic thiocyanate after reaction with a sulfur donor, such as thiosulfate. The purpose of this study was to determine the kinetic parameters of rhodanese with thiosufate and cyanide as substrates, and also the inhibition action of 2-oxoglutarate on this enzymatic reaction. This work shows that the Michaelis constants for both substrates (thiosulfate and cyanide), the effect of teperature on rhodanese reaction, and the inhibition parameters can be easily performed by EMMA methodology combined with a partial filling technique. The method can be used not only to estimate KI but also for the determination of the inhibition type of 2-oxoglutarate action on rhodanese reaction. Compared to spectrophotometric and other discontinuous assays, the method is rapid, can be automated, does not need expensive radiolabeled substrates and requires only small amounts of reagents which is especially important in the case of enzymes (injection volume of analytes is in the order of nanoliter). In consequence the EMMA methodology could serve as a progressive tool of modern enzymology in context of metabolomic research. |
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