Aldoxime dehydratase-nitrile

Microsomal membranes containing L-amino acid iV-monooxygenase, iV-hydroxy amino acid dehydrogenase (oxy-dative decarboxylat-ing), aldoxime dehydratase, nitrile monooxygenase (D 9.3)... 

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). 

NITRILE SYNTHESIS USING A NEW ENZYME, ALDOXIME DEHYDRATASE... 

Aldoximes are prepared from aldehydes and hydroxylamine by condensation reaction, and the dehydration reaction of aldoxime is one of the most important methods of nitrile synthesis in organic chemistry." We speculated that it would become one of the most important examples in Green Chemistry if the dehydration reaction could be realized by an enzymatic method, and started studies on a new enzyme, aldoxime dehydratase, and its use in enzymatic nitrile synthesis. Furthermore, we clarified the relationship between aldoxime dehydratase and nitrile-degrading enzymes in the genome of the microorganisms and the physiological role of the enzyme. 

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). 

Synthesis of nitriles from aldoxime with aldoxime dehydratase ... 

Reaction studies include cyanations using hydroxy nitrile lyases, hydrolysis of amides using acylases, amidases or lipases, and even dehydration reactions of aldoximes to nitriles using aldoxime dehydratase. This reaction is quite... 

L-Amino acid iV-monooxygenase 2 iV-hydroxy amino acid dehydrogenase (oxydative decarbo-xylating) 3 aldoxime dehydratase 4 nitrile monooxygenase 5 glucosyltransferase... 

Kato, Y., Yoshida, S., Xie, S.-X., and Asano, Y. (2004) Aldoxime dehydratase co-existing with nitrile hydratase and amidase in the iron-type nitrile hydratase-producer Rhodococcus sp. N-771. J. Biosci. Bioeng., 97, 250-259. 

In an aqueous medium, hydrolysis proceeds faster than dehydration because water is in large excess. However, in some cases, dehydration is preferred over hydrolysis. Remarkable results were reported by Kato et al. (Fig. 10.34), who demonstrated that aldoxime dehydratase from Bacillus sp. efficiently converted aldoximes into the corresponding nitriles in water. ... 

Dehydration of Aldoximes Forming (Chiral) Nitriles Using an Aldoxime Dehydratase... 

An enzyme being complementary to a nitrile hydratase, which catalyzes water addition to a nitrile, is an aldoxime dehydratase as a biocatalyst being capable to eliminate water from an oxime moiety, thus leading to the formation of a nitrile. Such aldoxime dehydratases are also synthetically useful as demonstrated by the Asano group who applied an aldoxime dehydratase from a Bacillus sp., for example, for the dehydration of Z-phenylacetaldoxime to produce phenylacetonitrile [37-41], For this substrate, the overexpressed aldoxime dehydratase showed a high activity of 14000U/1 of fermentation culture of a developed recombinant E. coli strain [3 . In addition, numerous other transformations of aromatic and aliphatic aldehydes have been reported [37 1],... 

On the other hand, 3-phenylpropionitrile was synthesized from Z-3-phenyl-propionaldoxime (0.75 M) in a quantitative yield (98gP ) by the use of cells of E. coli JM 109/pOxD-9OF, a transformant harboring a gene for a new enzyme, phenylacetaldoxime dehydratase, from Bacillus sp. strain OxB-1. Other arylalkyl- and alkyl-nitriles were also synthesized in high yields from the corresponding aldoximes. Moreover, 3-phenylpropionitrile was successfully synthesized by the recombinant cells in 70 and 100% yields from 0.1 M unpurified P/Z-3-phenylpropionaldoxime, which is spontaneously formed from 3-phenylpropionaldehyde and hydroxylamine in a butyl acetate/water biphasic system and aqueous phase, respectively. 

Synthesis of a chiral nitrile via kinetic resoiution of a racemic -aldoxime with a recombinant whoie cell-catalyst containing an aidoxime dehydratase. 

---