Production,Purification, and Characterization of D-Aminoacylase from Alcaligenes xylosoxydans subsp. xylosoxydans A-6

The best inducers for D-aminoacylase from Alcaligenes xylosoxydans subsp. xylosoxydans A-6 (Alcaligenes A-6) were a poor substrate, N-acetyl-;-methyl-D-leucine, and an inhibitor, N-acetyl-D-alloisoleucine. The enzyme has been homogeneously purified. The molecular weight of the native enzyme was estimated to be 58,000 by gel filtration. A subunit molecular weight of 52,000 was measured by SD8–PAGE, indicating that the native protein is a monomer. The isoelectric point was 5.2. The enzyme was specific to the D-isomer and hydrolyzed N-acetyl derivatives of D-leucine, D-phenylalanine, D-norleucine, D-methionine, and D-valine, and also N-formyl, N-butyryl, and N-propionyl derivatives of D-leucine. The K_m for N-acetyl-D-leucine was 9.8mM. The optimum pH and temperature were 7.0 and 50°C, respectively. The stabilities of pH and temperature were 8.1 and 40°C. D-Aminoacylases from three species of the genus Alcaligenes differ in inducer and substrate specificities, but are similar with respect to molecular weight and N-terminal amino acid sequence.