ANALYTICAL USES OF IMMOBILIZED ENZYMES

Abstract

This chapter presents the analytical uses of immobilized enzymes. The immobilized enzyme can be used analytically in the same way that the soluble enzyme is used, that is, to determine the concentration of a substrate that is acted upon by the enzyme, an inhibitor that inactivates the enzyme, or an activator that provides acceleration in enzyme activity. Two major techniques can be used to immobilize an enzyme are: (1) the chemical modification of the molecule by the introduction of insolubilizing groups. This technique, resulting in a chemical tying down of the enzyme, is in practice sometimes difficult to achieve because the insolubilizing groups can attach across the active site destroying the activity of the enzyme; and (2) the physical entrapment of the enzyme in an inert matrix, such as starch or polyacrylamide gels. Physical entrapment techniques offer advantages of speed and ease of preparation. The chapter also describes an electrical transducer for urea. The design of the analytical device takes advantage of the high sensitivity of the Beckman 39137 cation electrode and the specificity associated with enzyme analysis.