Enzymes commercially available

Chirazymes. These are commercially available enzymes e.g. lipases, esterases, that can be used for the preparation of a variety of optically active carboxylic acids, alcohols and amines. They can cause regio and stereospecific hydrolysis and do not require cofactors. Some can be used also for esterification or transesterification in neat organic solvents. The proteases, amidases and oxidases are obtained from bacteria or fungi, whereas esterases are from pig liver and thermophilic bacteria. For preparative work the enzymes are covalently bound to a carrier and do not therefore contaminate the reaction products. Chirazymes are available form Roche Molecular Biochemicals and are used without further purification. 

The only commercially available enzyme, FruA from rabbit muscle (class 1), is the most widely investigated, however, it is also the most sensitive under commonly used reaction conditions4. The other types, which can be isolated from overexpressing bacterial sources5-8, typically... 

A strategy to access lactones via enzymatic hydrolysis of y- and /3-hydroxy aliphatic nitriles to their corresponding acids with subsequent internal esterification was applied using commercially available enzymes from BioCatalytics Inc. A number of y- and /3-hydroxy aliphatic nitrile substrates (Table 8.11) were evaluated, with the greatest selectivity observed with y-hydroxy nonanitrile, which was converted by nitrilase NIT1003 to the precursor of the rice weevil pheromone in 30% yield, 88% ee with an enatiomeric ratio of = 23 [90],... 

More than 90% of commercially available enzyme-based biosensors and analytical kits contain oxidases as terminal enzymes responsible for generation of analytical signal. These enzymes catalyze oxidation of specific analyte with molecular oxygen producing hydrogen peroxide according to the reaction ... 

Table I. The Major Commercially Available Enzymes and Estimated Market Size...

Most of the amperometric flow-through biosensors based on commercially available enzymes are employed to measure consumed or released oxygen by using a Clark electrode or a solid-state electrode to monitor the hydrogen peroxide formed or an enzymatically reduced acceptor. 

The advantage of the use of alkaline phosphatase (AP) lies in the high purity of commercially available enzyme. But it is difficult to get such highly specific activities as for HRP, because there is no simple procedure for separation of unbound antibodies from the conjugate. 

The number of commercially available activated carriers for covalent attachment is therefore small in comparison to commercially available enzyme adsorbent materials. 

Commercially available enzyme-conjugated secondary antibody is usually diluted 1/200 to 1/2000 (i.e., 20 pl/ml to 2 pl/ml) prior to use (Harlow and Lane, 1988). 

M Hagg. Effect of various commercially available enzymes in the liquid chromatographic determination with external standardization of thiamine and riboflavin in foods. J AOAC Int 77 681-686,1994. 

In a different approach, the hydrolase-catalyzed kinetic resolution of chiral acetates was studied using a high-throughput ee assay also based on an enzyme-coupled test, the presence of a fluorogenic moiety not being necessary [16]. The assay is based on the idea that the acetic acid formed by hydrolysis of a chiral acetate can be transformed stoichiometrically into NADH in a series of coupled enzyme reactions using commercially available enzyme kits (Fig. 9.10). The NADH is then... 

Wigfield, Y.Y. and R. Grant (1993). Analysis for atrazine in fortified cornmeal and corns using a commercially available enzyme immunoassay microtiter plate. Bull. Environ, Contam. Toxicol., 51 171-177. 

Another major benefit of the purity of CLCs relates to the fact that many commercially available enzyme products actually contain more than one enzyme, and these contaminating enzymes can often lead to undesired side reactions. In the case of a resolution this can mean the difference between success and failure. For example, in the resolution of racemic ketoprofen by ester hydrolysis (Fig. 1), the enantioselectivity using crude Candida rugosa lipase is poor (E = 5). 

Paper Separations. The separation of the inorganic components from the remainder of the paper by differential centrifugation of a suspension of the paper dispersed in a fluid before X-ray examination may also be useful. Insoluble components could be obtained directly, while soluble components would have to be extracted and isolated by evaporation. However, this dispersion process would probably lead to a modification of the components or their structures. The same is true for the possible removal of the cellulose by hydrolysis in the presence of commercially available enzymes. 

As discussed in this chapter, the use of microorganisms or commercially available enzymes to carry out biotransformations is well-established. Numerous routes have been developed to prepare chiral... 

Fig. 30.11. Commercially available enzyme granules. (Courtesy Genencor International.)...

Malic dehydrogenase—Prepare this reagent just before use and store at 4°C. Dilute commercially available enzyme in 0.10 M potassium phosphate buffer, pH 7.5, in which 1 mg/ml bovine serum albumin has been dissolved. The final concentration of malic dehydrogenase should be 200 units/ml. Prepare a total of 20 ml of this reagent. 

In organoleptic studies no significant changes in odour and taste could be found when the commercially available enzyme preparations were used even at concentrations many times the normal level. 

Almost 3200 different enzymes have been listed and categorized by the International Union of Biochemistry and Molecular Biology in its last report in 1992. An encyclopaedic description of more than 7000 commercially available enzymes can be found in Ref [36]. Table 10.2 collects some industrial enzymes suppliers. Enzymes exhibiting the same catalytic function are known as homologous enzymes and they fall into two classes heteroenzymes and isoenzymes. The first group includes enzymes derived from different sources but which catalyse identical reactions, yet show different chemical and kinetic characteristics. A comprehensive enzyme information system, termed BRENDA, is available via the Internet (http //www.brenda.uni-koeln.de). 

Although some commercially available enzymes are linkage specific, the majority of linkages cannot be defined solely using this approach and/or using the chemical approaches. Hence, linkage analysis experiments are often necessary for rigorous stmeture analysis. 

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