Nitrilase induction

Thermally stable nitrilase from Streptomyces sp. MTCC 7546 was induced by benzonitrile enrichment. While discovered by induction with aromatic nitrile, the enzyme was shown to exhibit a strong preference for aliphatic nitriles, with as high as 30-fold greater activity with aliphatic substrates compared with benzonitrile. The enzyme displays optimal activity at pH 7 and 50 °C [56]. 

Plug these flasks with cotton plugs and autoclave at 15 psi pressure for 20 min. Transfer 2 mL of preculture as prepared above into each of the flasks. Add 0.2 mL of filter sterile propionitrile (filter 5 mL of propionitrile using 0.22 pm filter into a sterile tube) into each flask as inducer for the induction of nitrilase in G. terrae NDB 1165 cells. Incubate these at 30 °C in a gyratory shaker (180 rpm) for 24 h. 

Goldlust, A. and Bohak, Z. 1989. Induction, purification, and characterization of the nitrilase of Fusarium oxysporum f. sp. melonis. Biotechnology and Applied Biochemistry, 11 581-601. 

A method of efficient induction of fungal nitrilases in wild strains was established and seems to be of wide application throughout this enzyme group. However, heterologous expression of fungal nitrilases remains to be solved in order to facilitate the use of these enzymes in industrial biotechnology. To what extent the desirable properties (broad substrate specificity, thermostability, chemoselectivity and enantioselectivity) can be improved by mutagenesis of these enzymes should also be examined. 

Recently we determined that two R. rhodochrous strains (A29 and A99) expressed nitrilase activity after induction. These strains were capable of enantioselectively hydrolyzing racemic 3-amino-3-phenylpropanenitrile directly to the corresponding (R)-3-amino-3-phenylpropanoic acid with >95% ee (Table 14.1) in a kinetic resolution. Various inhibitors were used, that indicated the observed hydrolytic activity was due to the presence of a nitrilase rather than a nitrile hydratase and amidase pair [47]. 

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