Determination of rhodanese enzyme activity by capillary zone electrophoresis

Latest news about the sulfurtransferase protein family of higher plants

Sulfurtransferases/rhodaneses (Str) comprise a group of enzymes widely distributed in all phyla which catalyze in vitro the transfer of a sulfur atom from suitable sulfur donors to nucleophilic sulfur acceptors. The best characterized Str is bovine rhodanese (EC 2.8.1.1) which catalyses in vitro the transfer of a sulfane sulfur atom from thiosulfate to cyanide, leading to the formation of sulfite and thiocyanate. Plants as well as other organisms contain many proteins carrying a typical rhodanese pattern or domain forming multi-protein families (MPF). Despite the presence of Str activities in many living organisms, the physiological role of the members of this MPF has not been established unambiguously. While in mammals these proteins are involved in the elimination of toxic cyanogenic compounds, their ubiquity suggests additional physiological functions. In plants, Str are localized in the cytoplasm, mitochondria, plastids, and nucleus. Str probably also transfer reduced sulfur onto substrates as large as peptides or proteins. Several studies in different organisms demonstrate a protein-protein interaction with members of the thioredoxin MPF indicating a role of Str in maintenance of the cellular redox homeostasis. The increased expression of several members of the Str MPF in various stress conditions could be a response to oxidative stress. In summary, data indicate that Str are involved in various essential metabolic reactions.

Integration of short-end injection mode into electrophoretically mediated microanalysis

The possibility of integration of the short-end injection mode in the EMMA methodology is demonstrated in this work on the kinetic studies of haloalkane dehalogenase and rhodanese enzymatic reactions. The essential validations of the EMMA methods combined with the short-end and long-end injection modes were performed first to confirm their accuracy. The qualitative and quantitative parameters of both approaches such as repeatabilities of migration times and peak areas, limits of detection and correlation coefficients were in acceptable ranges. In addition, estimated Michaelis constants for the corresponding substrate(s) were comparable being in accordance with previous literature data. Moreover, the ping-pong reaction mechanism of rhodanese reaction was confirmed by means of both injection modes. This combination thus preserves the benefits of these instrumental approaches. Whereas the short-end injection procedure brought 5-6.5 times reduction of the analysis time and 2.5-4 times increase of the sensitivity, the EMMA methodology allowed full automatization of the assays while the whole kinetic studies needed only 20 microl of corresponding enzyme preparation.

Determination of cyanide in microliter samples by capillary electrophoresis and in-capillary enzymatic reaction with rhodanese

This paper describes a method for the determination of cyanide using in-capillary enzymatic reaction with rhodanese. Poorly absorbing cyanide is in rhodanese reaction transformed into highly absorbing thiocyanate that is further separated by capillary electrophoresis (CE) and determined spectrophotometrically at 200 nm. Cyanide is thus estimated indirectly from the result of thiocyanate quantification and moreover, it can be easily determined with sufficient sensitivity by means of CE apparatus equipped with common UV detector. The linear detection range for concentration versus peak area for the assay is from 15 to 500 microM (correlation coefficient 0.997) with a detection limit of 3 microM and a limit of quantitation 9 microM. The inter-day reproducibility of the peak area was below 3.2% and the inter-day reproducibility of the migration time below 0.1%. The method is relatively rapid, simple and can be easily automated. Moreover, only limited amount of the sample is required.

Determination of enzymatic activity by capillary electrophoresis

Enzymes are biological catalysts that play an important role in biochemical reactions necessary for normal growth, maturation and reproduction through whole live world. Their accurate quantitation in biological samples is important in many fields of biochemistry, not only in routine biochemistry and in fundamental research, but also in clinical and pharmacological research and diagnosis. Since the direct measurement of enzymes by masses is impossible, they must be quantified by their catalytic activities. Many different methods have been applied for this purpose so far. Although photometric methods are undoubtedly the most frequently used, separation methods will further gain their position in this field. The article reviews different possibilities for the assay of enzymatic activity by means of capillary electrophoresis (CE). Both the off-line and on-line enzyme assays based on CE are discussed.

Separation methods applicable to the evaluation of enzyme-inhibitor and enzyme-substrate interactions

Enzymes catalyze a rich variety of metabolic transformations, and do so with very high catalytic rates under mild conditions, and with high reaction regioselectivity and stereospecificity. These characteristics make biocatalysis highly attractive from the perspectives of biotechnology, analytical chemistry, and organic synthesis. This review, containing 128 references, focuses on the use of separation techniques in the elucidation of enzyme-inhibitor and enzyme-substrate interactions. While coverage of the literature is selective, a broad perspective is maintained. Topics considered include chromatographic methods with soluble or immobilized enzymes, capillary electrophoresis, biomolecular interaction analysis tandem mass spectrometry (BIA-MS), phage and ribosomal display, and immobilized enzyme reactors (IMERs). Examples were selected to demonstrate the relevance and application of these methods for determining enzyme kinetic parameters, ranking of enzyme inhibitors, and stereoselective synthesis and separation of chiral entities.

Inhibition study of rhodanese by means of electrophoretically mediated microanalysis

A combination of the electrophoretically mediated microanalysis methodology with a partial filling technique was applied for the inhibition study of bovine liver rhodanese by 2-oxoglutarate. In this set-up, part of the capillary is filled with the best buffer for the enzymatic reaction, while the rest of the capillary is filled with the optimal background electrolyte for separation of substrates and products. The estimated value of K1 for 2-oxoglutarate was 3.62 x 10(-4) +/- 1.43 x 10(-4) M with respect to cyanide and 1.40 x 10(-3) +/- 1.60 x 10(-4) M with respect to thiosulfate. In addition, the type of inhibition was also evaluated. The findings of 2-oxoglutarate as the competitive inhibitor with respect to cyanide and as the uncompetitive inhibitor with respect to thiosulfate are in accordance with previous literature data.

Application of capillary zone electrophoresis to study the properties of rhodanese from Acidithiobacillus ferrooxidans

A new capillary zone electrophoretic method was applied to the assay of enzymic activity of rhodanese from Acidithiobacillus ferroxidans. The enzyme activity determined by capillary zone electrophoresis was compared with that determined by discontinuous spectrophotometry, the values obtained being in good agreement. The method was also used to evaluate Michaelis constants of cyanide and thiocyanate as substrates; a new approach was developed to solve the problem with variable ionic strength of the samples. The pH and temperature optima for the enzyme were also determined.

Fast analysis of antibacterial isothiazolones by capillary electrophoresis

Some technical aspects influencing the total time of CE analysis are discussed. A high throughput electrophoretic system based on micellar electrokinetic chromatography (MEKC) is demonstrated as an example. A short capillary, strong electric field, alkaline buffer (pH 9.5) generating strong electroosmotic flow, and parallel hydrodynamic pressure allow the separation of two uncharged isothiazolone derivatives within 45 s.

Analysis of thiocyanate in biological fluids by capillary zone electrophoresis

A new sensitive and simple method has been developed for the determination of thiocyanate in human serum, urine and saliva. The determinations were performed in a fused-silica capillary [64.5 cm (56 cm effective length) x 75 microm] using 0.1 M beta-alanine-HCl (pH 3.50) as a background electrolyte, separation voltage 18 kV (negative polarity), temperature of capillary 25 degrees C and direct detection at 200 nm. Serum samples were 10-times diluted with deionised water and deproteinised with acetonitrile in the ratio 1:2. Urine and saliva samples need only 20-fold dilution with deionised water. The proposed method was successfully applied to the determination of thiocyanate in various human serum, saliva and urine samples.

Determination of haloalkane dehalogenase activity by capillary zone electrophoresis

A new sensitive method has been developed for the determination of haloalkane dehalogenase activity. The enzymatic reactions were carried out directly in thermostatted autosampler vials and the formation of product - bromide or chloride ions - was monitored by sequential capillary zone electrophoresis runs. The determinations were performed in a 75 microm fused-silica capillary using 5 mM chromate, 0.5 mM tetradecyltrimethylammonium bromide (pH 8.4) as a background electrolyte, separation voltage 15 kV (negative polarity) and indirect detection at sample wavelength 315 nm, reference wavelength 375 nm for brominated and chlorinated substrates, respectively 0.1 M beta-alanine-HCl (pH 3.50) as a background electrolyte, separation voltage 18 kV (negative polarity) and direct detection at 200 nm for brominated substrates. The temperature of capillary was in both cases 25 degrees C. The method is rapid, can be automated, and requires only small amount of enzyme preparation and substrate.