Purification and characterization of aryl acylamidase from Nocardia globerula

Aryl acylamidase was purified from an extract of N-acetyl-o-toluidine-induced cells of Nocardia globerula IFO 13510 in ten steps. The purified enzyme appeared to be homogeneous from analysis by polyacrylamide gel electrophoresis. The enzyme has a molecular mass of approximately 126 kDa and consists of two subunits which are identical in molecular mass. The purified enzyme catalyzed the hydrolysis of N-acetyl-o-toluidine to o-toluidine and acetic acid at a rate of 47.7 mumol.min-1.mg-1 at 35 degrees C. It also catalyzed the hydrolysis of various anilide derivatives and esters, as well as the transfer of an acetyl group to aniline as an acetyl acceptor. The purified enzyme was sensitive to thiol reagents such as HgCl2 and p-chloromercuribenzoate. The amino-terminal sequence (28 amino acid residues) of the enzyme was determined. Based on the substrate specificity of this enzyme, the pathway intermediates involved in the conversion of n-acetyl-o-toluidine to 4'-hydroxy-N-acetyl-o-toluidine are discussed.