Purification and characterization of a novel metalloprotease from fruiting bodies of Oudemansiella radicata.

In this study, a 39-kDa metalloprotease was purified from a rare edible mushroom with health-promoting activities, Oudemansiella radicata, using a purification protocol which entailed anion exchange chromatography on DEAE-cellulose and Q-Sepharose columns and gel filtration by fast protein liquid chromatography on a Superdex 75 column. Some peptide sequences were obtained by LC-MS/MS analysis and one of the sequences, DAWIQADVNR, manifested 90% identity to Coprinopsis cinerea metalloprotease. The optimal reaction pH and temperature for Oudemansiella radicata protease were pH 7.0 and 50°C, respectively. The protease was purified 79-fold and demonstrated a specific protease activity of 2.42 U/mg. The K of the purified protease for the casein substrate was 0.65 mg/mL at pH 7.0 and 50°C. The activity of the protease was inhibited by Cd, Hg, Cu, Pb and Fe ions, but was enhanced by K, Mn and Fe ions. The marked suppression of the protease activity by EDTA indicates that the protease is a metalloprotease.