Group specificity, enzyme

The plasma fucosyltransferase to Gal produces a-L-Fuc-( 1—>-2)-Gal linkages, and is the H-dependent, blood-group-specific enzyme. Its selective inhibition by thiol-blocking agents has permitted its discrimination245 from other fucosyltransferases. 

As well as the enzyme 3a-hydroxysteroid dehydrogenase, a 7a-enzyme has been isolated from E. coli and a 12a enzyme from a strain of Clostridium (Ml). These group-specific enzymes can be used to measure the amounts and ratios of the three main bile acids (cholic, chenodeoxycholic, and deoxy-cholic acids) in bile specimens. Bioluminescent assays suitable for serum bile acid analysis have been described using 7a-hydroxysteroid dehydrogenase (R6) and 12a-hydroxysteroid dehydn enase (S12), as well as for the 3a enzyme (S13, S44). 

MacDonald, I. A., Williams, C. N., and Musial, B. C., 3a,7a, and 12a-hydroxy group specific enzymic analysis of biliary bile acids Comparison with gas-liquid chromatography. /. lipid Res. 20, 381-385 (1979). 

The 3a-, 7a-, and 12a-Hydroxy Group-Specific Enzyme Analysis of Biliary Bile Acids Comparison with Gas-Liquid Chromatography J. Lipid Res. 21(3) 381-385 (1980) ... 

Tyrosinase was shown to have a relatively narrow substrate selectivity (3). In this study we focus on one sensor of each type, namely on POD and CDH biosensors, since these are more general group-specific enzymes compared with tyrosinase and laccase. 

Since enzyme action depends on the closeness with which the structure of the enzyme and its substrate complement each other, most enzymes are stereochemically specific. They act on only one of a pair of optical isomers or, if both should be attacked, one reacts much more readily than the other. For example, maltase is a group-specific enzyme that attacks several other a-glucosides as well as maltose but has no effect on S-glucosides. 

Herbicidal Inhibition of Enzymes. The Hst of known en2yme inhibitors contains five principal categories group-specific reagents substrate or ground-state analogues, ie, rapidly reversible inhibitors affinity and photo-affinity labels suicide substrate, or inhibitors and transition-state, or reaction-intermediate, analogues, ie, slowly reversible inhibitors (106). 

There are many ligands and group-specific reagents that have been demonstrated to alter the properties of H,K-ATPase, and which are not clinically useful. For example, there is a variety of chemicals that have been used in studies on structure-function relations of H,K-ATPase and that inhibit the enzyme in vitro by modification of its amino [49,67,158], sulfhydryl [95,165,166] or carboxyl groups [140]. 

Some active materials are carriers for drugs (drug delivery systems), some have immobilized peptides to enable cell adhesion or migration, some are degradable by hydrolysis or by specific enzyme action. Some contain bioactive agents (e.g., heparin, thrombomodulin) to prevent coagulation or platelet activation while others incorporate bioactive groups to enhance osteo-conduction. Many include polyethylene oxide to retard protein adsorption and this is perhaps the closest we have come to a kind of inertness. 

Group specificity, in which the enzyme catalyzes reactions of only one type of functional group. 

---