A novel metalloprotease from the wild basidiomycete mushroom Lepista nuda

A 20.9-kDa metalloprotease was isolated from dried fruiting bodies of the wild basidiomycete mushroom Lepista nuda. The N-terminal amino acid sequence of the protease was seen to be ATFVLTAATNTLFTA, thus displaying no similarity with the sequences of previously reported metalloproteases. The protease was purified using a procedure that entailed ion-exchange chromatography on CM-Cellulose, Q-Sepharose, and Mono S, and FPLC-gel filtration on Superdex 75. The protease functioned at an optimum pH of 7.0 and an optimum temperature of 50 degrees C. It was also noted that the protease demonstrated a proteolytic activity of 1,756 U/mg toward casein. The Km of the purified protease toward casein was 6.36 mg/ml at a pH of 7.0 and with a temperature of 37 degrees C, whereas the Vmax was 9.11 microgram ml(-1) min(-1). The activity of the protease was adversely affected by EDTA-2Na, suggesting that it is a metalloprotease. PMSF, EGTA, aprotinin, and leupeptin exerted no striking inhibitory effect. The activity of the protease was enhanced by Fe2+, but was curtailed by Cd2+, Cu2+, Hg2+, Pb2+, Zn2+, and Fe3+ ions. The protease also exhibited inhibitory activity against HIV-1 reverse transcriptase with an IC50 value of 4.00 micrometer. The IC50 values toward hepatoma Hep G2 and leukemia L1210 cells in vitro were 4.99 micrometer and 3.67 micrometer, respectively.