Purification and partial characterization of a fibrinolytic protease in Pleurotus ostreatus

Abstract

Fibrinolytic protease activity was detected from a crude extract of the fruit body of Pleurotus ostreatus using the fibrin plate method. The enzyme was purified 52 fold through several column chromatography steps including gel filtration, hydrophobic phenyl Sepharose and anion exchanger Mono Q with a 5% recovery. The enzyme cleaved not only fibrin but also B_β and γ chain of human fibrinogen. There was no activity against the azocasein, azoalbumin and elastin substrate. The protease was specific for hydrophobic and bulky amino acids in the P'1 position. The enzyme was insensitive to PMSF, TPCK, leupeptin, pepstatin, iodoacetic acid, p-chloromercuribenzoate and E-64, indicating that it is not a class of serine protease, acid protease or cysteine protease. However, it was sensitive to metal chelating agents such as 1, 10-phenanthroline and EDTA. Phenanthro-line-inactivated enzyme was recovered by addition of Zn²⁺ or Co²⁺. The presence of Zn²⁺ was detected by ICP mass spectral analysis as 0.77 mol of Zn²⁺ per mol protease. The enzyme is likely to be a Zn²⁺ metalloprotease.

Key Words:

• fibrin
• fruit body
• metalloprotease
• mushroom
• zinc