Transformation of aliphatic and aromatic nitriles by a nitrilase fromPseudomonassp.

Abstract

A Pseudomonas sp. (S1) isolated from a garden soil possessed a unique nitrilase, which is capable of catalyzing the direct hydrolysis of both potassium and organic cyanides to their corresponding carboxylic acids and ammonia, without the formation of amide as an intermediate. The nitrilase was purified with 4.8% recovery in three steps from a cell extract of the strain. The relative mobility of the homogenous enzyme preparation in SDS and native polyacrylamide gels indicated molecular weight of 41 kDa, approximately. Pseudomonas sp. (S1) utilized all the nitriles as carbon and nitrogen sources. The enzyme was induced by both aliphatic and aromatic nitriles, while the aliphatic olefinic nitrile - acrylonitrile was the most suitable substrate. The nitrilase also catalyzed the hydrolysis of acetonitrile, adiponitrile, benzonitrile, butyronitrile, glutaronitrile, phenylacetonitrile, succinodinitrile, and potassium cyanide, with the formation of ammonia and the corresponding carboxylic acids. The Michaelis-Menten constant, Km, of the partially purified nitrilase for acetonitrile, acrylonitrile, adiponitrile, benzonitrile, and potassium cyanide presented values of 11.26, 5.88, 10.28, 12.27, and 0.75 mM, respectively.Key words: nitriles, enzyme kinetics, nitrilase, partial purification, Pseudomonas sp.