Nitrile hydrolase Nitrilase

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. 

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. 

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... 

On the other hand, nitrilases operate by a completely different mechanism (Scheme 2.101). They possess neither coordinated metal atoms, nor cofactors, but act through an essential nucleophilic sulfhydryl residue of a cysteine [641, 642], which is encoded in the nitrilase-sequence motif Glu-Lys-Cys [643]. The mechanism of nitrilases is similar to general base-catalyzed nitrile hydrolysis Nucleophihc attack by the sulfhydryl residue on the nitrile carbon atom forms an enzyme-bound thioimidate intermediate, which is hydrated to give a tetrahedral intermediate. After the elimination of ammonia, an acyl-enzyme intermediate is formed, which (like in serine hydrolases) is hydrolyzed to yield a carboxyhc acid [644]. 

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