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

Abstract

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_m 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 Cd²⁺, Hg²⁺, Cu²⁺, Pb²⁺ and Fe³⁺ ions, but was enhanced by K⁺, Mn²⁺ and Fe²⁺ ions. The marked suppression of the protease activity by EDTA indicates that the protease is a metalloprotease.

Keywords: Oudemansiella radicata; edible mushroom; protease; purification.