Enzymes as reagents in clinical chemistry

Abstract

Clinical chemistry is concerned with the measurement of substances in biological matter, predominantly blood, serum or plasma. Significant, though small, changes may take place as a prelude to a life-threatening situation. Therefore analytical techniques in clinical chemistry must be sensitive, specific and rapid. Many features of an enzyme-catalysed reaction are incorporated in the design of diagnostic reagents. The specificity of an enzyme may be employed to measure a substrate, or to remove interferents in another reaction. The measurement of substances that act as cofactors, inhibitors or activators can be achieved by the use of the appropriate enzyme. Finally, the enzyme, as a catalyst, can be used as a label in various immunoassay techniques. Clinical chemistry tests are carried out in a wide variety of environments, from the large laboratory undertaking many hundreds of analyses down to a clinic performing only a few tests. Enzymes are therefore employed in analytical systems based on widely differing presentations. Thus enzymes may be employed in a solution medium, immobilized on a surface of the reaction vessel or in a reagent strip. The requirements imposed on the reagent enzyme may be different in all of these situations.

Bacillus

“…Perhaps the most commercially important of these is glucose isomerase, which is discussed in detail in Section 3.1. Many enzymes from Bacillus are used as reagents in clinical chemistry, particularly those isolated from thermophilic species which have superior stability (Atkinson, 1983;Price, 1983), e.g., glycerokinase glucokinase (Hengartner and Zuber, 1973;Goward et ai., 1986), and leucine dehydrogenase (Oshima and Soda, 1985). This same stability also accounts for the wide- Wilson and Young, 1975Sugisaki et aI., 1982Sugisaki et al, 1982Bingham et al, 1978Duncan et al, 1978Duncan et aI., 1978Catterall and Welker, 1977Lautenberger et al, 1980 spread use of enzymes from thermophilic Bacillus strains in structural studies of enzymes, where, for example, the crystal structure of tyrosyl and tryptophanyl tRNA synthetases from B. stearothermophilus were determined because the enzymes from E. coli were insufficiently stable.…”

Nuclease-assisted selection of slow-off rate aptamers

“…Bioreceptors such as antibodies and aptamers have revolutionized fields including medicine ( 1 , 2 ), forensics ( 3 ), biomedical engineering ( 4 ), and materials science ( 5 ) by enabling selective identification ( 6 , 7 ), sequestration ( 8 – 10 ), or functional modulation ( 11 , 12 ) of specific molecular targets. They are often characterized on the basis of their affinity for ligands, which is measured thermodynamically in terms of the equilibrium dissociation constant ( K d ).…”

Biotechnologically relevant enzymes from Thermus thermophilus

“…These days, the total market of bacterial diagnostic enzymes has increased tenfold compared to 5 years ago. The stability that can be achieved with enzymes from thermophilic microorganisms will stifle one of the major criticisms of enzymes as reagents (Price 1983). …”