NEW MATERIAL:An enzyme having the following enzymological properties. Activity, acting to N-acetyl-D,L-amino acid to isolate L-amino acid; substrate specificity, acting exclusively to the L-isomer of acetylated amino acid, inert to the D-isomer, and exhibiting higher activity to N-acetyl-L-phenylalanine than N-acetyl-methionine; optimum pH, about 8.0; pH stability, stable at 5.0W10.0pH by the treatment at 50°C for 10min; optimum temperature, about 60°C; temperature stability, keeping the activity completely by the treatment at 70°C for 10min and keeping 90% of the initial activity by the treatment at 70°C for 30min.

USE: A heat-resistant aminoacylase SK-1 useful for the optical resolution of D,L- amino acid.

PREPARATION: A bacterial strain belonging to Bacillus genus and capable of producing heat-resistant aminoacylase SK-1 (e.g. Bacillus stearo-thermophilus IFO 12983) is inoculated in a medium and cultured at 50W65°C for 5W20hr under agitation and aeration.