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Biotransformation by enzymes of the nitrile metabolism

( L. Martínková, M. Chmátal, V. Křen, M. Pátek, L.Rucká, J. Nešvera)

Nitrile hydrolysis is an important step in the synthesis of carboxylic acids and amides (building blocks for the synthesis of fine and pharmaceutical chemicals). It has been traditionally carried out under extreme conditions (strong acids or bases, high temperatures). The disadvantages of this method are high energy costs, low yields and missing selectivities.

However, the enzymes of the nitrile metabolism (Figure 1) perform these reactions under mild conditions, enantio- or regioselectively and with high yields. These enzymes consist of nitrilases and nitrile hydratases which transform nitriles into carboxylic acids and amides, respectively. Amides are then hydrolyzed by amidases. The synthesis of nitriles from aldoximes is catalyzed by aldoxime dehydratases. *

nitrile-hydrolyzing enzymes

Figure 1: Reactions catalyzed by enzymes of nitrile metabolism

The focus of our work is on the acquisition of new representatives of the aforementioned enzymes, e.g. by mining gene databases (GenBank) and expressing the selected, artificially synthesized genes in . In this way a set of more than 15 nitrilases from filamentous fungi was constructed. These catalysts (cells, purified enzymes) were used in the synthesis of alfa-hydroxy acids (building blocks, cosmetics) or new derivatives of taxol (anticancer drug) from the corresponding nitriles.

Some bacterial nitrilases were prepared analogously and proved useful in the biotransformation of benzonitrile herbicide residues into less toxic and biodegradable carboxylic acids (Figure 2).

Figure 2: Enzymatic detoxication of benzonitrile herbicides

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Institute of Microbiology - Czech Academy of Sciences