Nitrile Hydratase and Amidase Cascade Substrate Selectivity

Nitrile Hydratase and Amidase Cascade Substrate Selectivity 

Winkler and coworkers tested the substrate spedfidty of three different Rhodococcus sp. strains on five- and six-membered cis- or tranx-aUcydic p-aminonitriles. They found that the five-membered substrates were hydrolyzed significantly faster than their corresponding six-membered counterparts, and the reaction products from the tranx-aminonitriles were formed considerably faster than for the cis-substrates [62]. In addition, the Rhodococci exhibited far greater enantioselectivity for the 

In contrast to these results, the five-membered trans-aminonitriles yielded transamides of high enantiopurity, whereas the respective acid products had poor enantiomeric excess values. The results support an enantioselective amidase and a nonselective nitrile hydratase, particularly for the benzyl protected substrate, where all the nitrile was converted [62]. 

Our original studies with unprotected P-hydroxynitriles showed that these compounds were hydrolyzed by R. rhodochrous ATCC BAA-870, expressing a benzamide-induced cobalt type nitrile hydratase, to the corresponding amides and acids [11]. The formation of the amide implies a nitrile hydratase and amidase system (although sometimes nitrilases can release partially hydrolyzed substrates as amides [63]). Further studies in our laboratories demonstrated that the system was indeed a nitrile hydratase and amidase cascade reaction functioning via a two 

Functional groups Reaction catalyzed Selectivity Organism 

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