ABSTRAKT

A novel protease was isolated from Coprinopsis atramentaria, which is, to our knowledge, the first macromolecule to be purified from this species. The protease, referred to as CAP, was purified through the use of ion exchange chromatography on sulphopropyl-sepharose, diethylaminoethyl-cellulose, Q-Sepharose, and gel filtration on a Superdex 75 column. CAP is a monomelic protein with a molecular mass of 32 kDa. The maximum activity of CAP was detected at pH 7.0 and 50°C. The preferred pH of CAP demonstrated that it was a neutral protease. Kinetic constants were determined under optimal reaction conditions, using 1% casein as the substrate. We found K_m and V_max values of 7.98 mg · mL^-1 and 215 μg · mL^-1 · min^-1, respectively. Among the various metal ions tested, Pb²⁺, Zn²⁺, Mn²⁺, Hg²⁺, Cu²⁺, and Cd²⁺ exerted dose-dependent inhibitory actions, whereas Mg²⁺ exhibited a promoting action at all concentrations tested. Eight inner peptide sequences were detected by liquid chromatography on an LTQ-Orbitrap mass spectrometer and were identified using the Basic Local Alignment Search Tool, which contains proteases from other sources. Alignment results showed that 2 of them were homologous to fungal cysteine proteases. The other 5 peptide sequences also shared similarities with proteases of other origins. The isolation of a novel protease from C. atramentaria in this study not only expands the sources of proteases but also provides further information about this fungus.