Purification and characterization of an extracellular protease from Rhizoctonia cerealis

Rhizoctonia cerealis could secrete several extracellular proteases when grown in liquid medium with wheat cell walls as the sole carbon and nitrogen source.A kind of protease was purified after ammonium sulfate precipitation,SP-Sepharose Fast Flow chromatography,Phenyl high-sub-Sepharose Fast Flow chromatography and Sephadex G-75 chromatography.It appeared as a single band corresponding to molecular weight MWof approximately 40 kD on SDS-PAGE with silver staining.It showed high activities against the trypsin substrate Benz-Phe-Val-Arg-NA,and also the substrates D-Val-Leu-Arg-NA,Benz-Pro-Phe-Arg-NA and D-Val-Phe-Lys-NA.It was strongly inhibited by aprotinin,leupeptin,soybean trypsin inhibitor and partly inhibited by PMSF,indicating that it is quite probably a trypsin-like protease.