Nitrile hydrolase

Kobayashi, M. and Shimitzu, S. 2000. Nitrile hydrolases. Current Opinion in Chemical Biology, 4 95-102. 

Hydrolase, 1041-1042 Hydrolysis, 792 amides, 814-815 biological, 809-810, 815 esters. 809-811 fats. 809-810 nitriles, 768-769 proteins. 815... 

Katayama Y, Y Matsushita, M Kaneko, M Kondo, T Mizuno, H Nyunoya (1998) Cloning of genes coding for the three subunits of thiocyanate hydrolase of Thiobacillus thioparus THI 115 and their evolutionary relationships to nitrile hydratase. J Bacterial 180 2583-2589. 

Hydrolases lipase, protease, esterase nitrilase, nitrile hydratase glycosidase, phosphatase hydrolysis reactions in H20... 

The MS assay has also been applied successfully in the directed evolution of enantioselective epoxide hydrolases acting as catalysts in the kinetic resolution of chiral epoxides [35]. Moreover, Diversa has recently employed the MS-based technique for desymmetrization of a prochiral dinitrile catalyzed by mutant nitrilases [36]. In this industrial application one of the nitrile moieties was labeled with 15N, which means that the two pseudo enantiomeric products differ by only one mass unit. 

Hydrolases catalyse the hydrolysis of esters, amides and nitriles under mild conditions. As mentioned above, they also display an often-remarkable enantioselec-tivity. This opens the opportunity to employ these enzymes for the preparation of enantiopure compounds. This desymmetrization has been reviewed [16-24] and different approaches [25-27] are possible. 

Instead of starting with racemic starting material it is also possible to use symmetric substrates [25]. The hydrolase selectively catalyses the hydrolysis of just one of the two esters, amides or nitriles, generating an enantiopure product in 100% yield (Scheme 6.7). No recycling is necessary, nor need catalysts be combined, as in the dynamic kinetic resolutions, and no follow-up steps are required, as in the kinetic resolutions plus inversion sequences. Consequently this approach is popular in organic synthesis. Moreover, symmetric diols, diamines and (activated) diacids can be converted selectively into chiral mono-esters and mono-amides if the reaction is performed in dry organic solvents. This application of the reversed hydrolysis reaction expands the scope of this approach even further [22, 24, 27]. 

Very few reports are available for the enzymatic surface modification of synthetic fibers. Peroxidase, lipase, cutinase, nitrilase, nitrile hydratase, amidase, protease, and hydrolase have been reported for the surface modification of synthetic polymers (Table 4.1). 

Nitrilases and amidases belong to the class of hydrolases and nitrile hydratase belongs to the class of lyase. Nitrilases are an important class of nitrilase superfamily that convert nitrile to the corresponding carboxylic acids and ammonia, whereas nitrile hydratase first converts into the corresponding amide and then this amide is transformed by amidase. There are very few reports for the surface modification of PAN and PA for increasing its hydrophilicity using nitrilases, nitrile hydratases, and amidases. 

The enzymatic hydrolysis of nitriles to yield either the corresponding amides or carboxylic adds has been studied in some detail over the last 10 yr (70,71). The enzymatic hydrolytic cleavage of nitriles can be achieved by two types of hydrolase nitrile hydratase or nitrilase (Fig. 23). Nitrile hydratase has been commerdally exploited for the production of various amides, the most notable being acrylamide (10-12,71,72). 

The two enzyme classes nitrile hydratases (RCN + H20 — RCONH2) and nitrilases (RCN + 2H20 —y RCOOH + NH3) actually belong to two distant groups in the EC system, with the hydratases being classified as lyases (EC 4.2.1.84) and nitrilases as hydrolases (EC 3.5.5.1). Microorganisms that produce a nitrile hydratase also seem to produce amidases, which enable them to convert nitriles into carboxylic acids in a two-step reaction. Actually, amidase side-activity can be a problem with commercial nitrile hydratase preparations (if the target structure is the amide). Nitrilases, however, hydrolyze the nitrile without the formation of a free amide intermediate. 

Microorganisms which produce a nitrile hydratase also seem to synthesize one or more amidase enzymes [linear amide hydrolase (E.C. 3.5.1)] thus enabling them to hydrolyze nitriles to the corresponding acids in a two-step reaction ... 

SP 361 SP 409 Immobilized enzyme mixture from Rhodococcus sp. containing nitrilase, nitril hydratase,esterase, epoxide hydrolase and amidase activity discontinued... 

Hydrations of nitriles amides C=C Rhodococci, microbial nitrilases, nitrile hydratases microbial amido hydrolases BY, Ec, Prm, fumarase... 

Most industrial enzymatic processes refer to reactions conducted by hydrolases in aqueous medium for the degradation of complex molecules (often polymers) into simpler molecules in conventional processes with limited added value (Neidelman 1991). Reasons underlying are clear since hydrolases are robust, usually extracellular and have no coenzyme requirements, which makes them ideal process biocatalysts. Enzyme immobilization widened the scope of application allowing less stable, intracellular and non-hydrolytic enzymes to be developed as process biocatalysts (Poulsen 1984 D Souza 1999), as illustrated by the paradigmatic case of glucose isomerase for the production of HFS (Carasik and Carroll 1983) and the production of acrylamide from acrylonitrile by nitrile hydratase (Yamada and Kobayashi 1996). 

There are many types of enzyme-catalysed hydrolysis reactions. In this chapter, the hydrolysis of esters and amides will be surveyed quite extensively, while the hydrolysis of nitriles and epoxides will be mentioned briefly at the end. The use of hydrolase enzymes in organic solvents will be discussed also, in connection with the preparation of esters and amides. 

Hydrolases 650 -180 Hydrolysis formation of esters, amides, lactones, lactams, epoxides, nitriles, anhydrides, glycosides, organohalides -I-++... 

Other, more complex applications of hydrolases, such as those involving the formation and/or cleavage of phosphate esters, epoxides, nitriles, and organo-halides, are described elsewhere in this book. In contrast to the group of proteases, esterases and lipases, they have had less impact on organic chemistry, although their synthetic potential should not be underestimated. 

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