Nitriles aldoximes

Enzymes in aldoxime-nitrile pathway versatile tools in biocatalysis... 

The discovery and exploitation of enzymes in aldoxime-nitrile pathway nitrile hydratase, amidase, nitrilase, aldoxime dehydratase, etc., are shown along with the use of methodologies, such as organic chemistry, microbial screening by enrichment and acclimation culture techniques, enzyme purification, gene cloning, molecular screening by polymerase chain reaction (PCR). 

We also found that the occurrence of aldoxime dehydratase is as wide as that for nitrile-degrading enzymes such as nitrile hydratase, amidase and/or nitri-lase. All of the nitrile degraders hitherto isolated contained aldoxime dehydratase activities. The author would like to propose that the pathway in which aldoximes are successively degraded via nitrile could be named as the aldoxime-nitrile pathway (Fig. 1). 

Notably, nitrile-degrading enzymes (e.g. nitrilase that converts the CN group to carboxylic acid, and nitrile hydratase that produces an amide function) have been described, and they co-exist with aldoxime-degrading enzymes in bacteria (Reference 111 and references cited therein). Smdies in this area led to the proposal that the aldoxime-nitrile pathway, which is implemented in synthesis of drugs and fine chemicals, occurs as a natural enzymic pathway. It is of interest that the enzyme responsible for bacterial conversion of Af-hydroxy-L-phenylalanine to phenacetylaldoxime, an oxidative decarboxylation reaction, lacks heme or flavin groups which are found in plant or human enzymes that catalyze the same reaction. Its dependency on pyridoxal phosphate raised the possibility that similar systems may also be present in plants . 

Dehydration of aldoximes. Nitriles are obtained when aldoximes are treated with TBS-Cl and imidazole in DMF. 

The data establishing aldoximes, nitriles and a-hydroxynltriles as intermediates in the pathway have been reviewed elsewhere (3). 

Kato, Y. and Asano, Y. (2006) Molecular and enzymatic analysis of the aldoxime-nitrile pathway in the gluta-ronitrile degrader Pseudomonas sp. K-9. Appl. Microbiol. Biotechnol., 70, 92-101. 

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