Enzyme analysis : cathepsin d as an example

In enzyme analysis, capillary electrophoresis (CE) offers the ease of product separation from the substrate, with the ability to use expensive reagents in microvolumes. In CE, enzymes can be measured either as mass (when they are present in high concentration) by direct light absorbency, or by catalytic activity. For example, the protease enzyme, savinase, which is used as an ingredient in washing powder, was determined directly by its absorbency at 200 nm (1). For catalytic activity measurements, the substrate, the product, or both can be measured in CE without the need for coupling reactions. Because of the increased sensitivity, most CE methods measure enzymes by their catalytic activity on a substrate. To accomplish this by CE, several approaches have been used.