Determination of ITPase activity by capillary electrophoresis

Capillary electrophoretic enzyme assays

In the past years, capillary electrophoresis has become a frequently used technique for enzyme assays due to the high separation efficiency and versatility as well as small sample size and low consumption of chemicals. The capillary electrophoresis assays can be divided into two general categories: pre-capillary (or offline) assays and in-capillary (or online) assays. In pre-capillary assays, the incubation is performed offline and substrate(s) and product(s) are subsequently analyzed by capillary electrophoresis. In in-capillary assays enzyme reaction and separation of the analytes are performed inside the same capillary. In such assays the enzyme is either immobilized or in solution. The latter techniques is also referred to as electrophoretically mediated microanalysis (EMMA) indicating that the individual steps of the incubation as well as analysis are performed via electrophoretic phenomena. This chapter describes both techniques using the deacetylation of acetyl-lysine residues in model peptides by sirtuin enzymes as well as the hydrolysis of acetylthiocholine by acetylcholinesterase as examples.

Advances in capillary electrophoretic enzyme assays

In recent years, capillary electrophoresis (CE) has become a frequently used tool for enzyme assays due to its well-recognized advantages such as high separation efficiency, short analysis time, small sample and chemicals consumption. The published applications cover all aspects of enzyme characterization and analysis including the determination of the enzyme activity, substrate and modulator characterization and identification, as well as the investigation of enzyme-mediated metabolic pathways of bioactive molecules. The CE assays may be classified into two general categories: (1) pre-capillary assays where the reactions are performed offline followed by CE analysis of the substrates and products and (2) online assays when the enzyme reaction and separation of the analytes are performed in the same capillary. In online assays, the enzyme may be either immobilized or in solution. The latter is also referred to as electrophoretically mediated microanalysis (EMMA). The present review will highlight the literature of CE-based enzyme assays from 2006 to November 2009. One section will be devoted to applications of microfluidic devices.

ITPase activity in dry blood spots is comparable with that in fresh erythrocytes

Inosine triphosphate pyrophosphohydrolase (ITPase) catalyzing the pyrophosphohydrolysis of inosine triphosphate, deoxyinosine triphosphate and xanthosine triphosphate is involved in the metabolism and tolerance of thiopurine drugs. ITPase activity plays an important role in the prediction of toxicity to thiopurine therapy. Activities in dry blood spots were compared with fresh erythrocytes. Samples were incubated with inosine triphosphate, then inosine monophosphate was determined by a capillary electrophoresis method. Calculated enzyme activities obtained from dry blood spots were in good accordance with activity in fresh erythrocytes.