Nitrilase molecular masses

In general, nitrilases contain a single type of subunit, the molecular mass of which has been assessed at 32—45 kDa in a number of purified enzymes (for a review see [5, 6]). The size of subunits in fungal nitrilases from A. niger KIO, F. solani Ol, and F. oxysporum f. sp. melonis is in this range (see Table 14.1). In this context, the 76-kDa size reported for the nitrilase subunit in F. solani IMI196840 [30] is exceptional [10]. 

Table 14.1 Subunit and holoenzyme molecular masses of nitrilases from filamentous fungi comparison with selected prokaryotic nitrilases, cyanide hydratases and cyanide dihydratase.

Nitrilases have been studied less than the nitrile hydratases. The enzymes appear as homomultimers, exhibiting a wide range of molecular masses. The reaction mechanism depicted in Fig. 12.1-2 has been proposed recently by Kobayashi et al. 2S. Several nitrilases have been found to be inhibited by reagents which bind to thiol groups, indicating that sulfhydryl groups are essential for the catalytic activity of... 

Ibuprofen [(iS)-2-(4-isobutylphenyl)propionic acid] has been prepared by resting cells of Acinetobacter sp. AK 226 [34]. Evidence for a single-step nitiilase-catalyzed reaction was obtained by the lack of an intermediate amide formation, the remaining R) nitrile (Fig. 12), and the inability to transform the racemic amide. The (S)-specific nitrilase was purified and characterized as a typical high molecular mass enzyme of 580 kDa [45]. 

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