Purification and characterization of an extracellular serine protease from the nematode-trapping fungus Dactylella shizishanna.

AIMS

To evaluate the production of an extracellular serine protease by Dactylella shizishanna and its potential as a pathogenesis factor.

METHODS AND RESULTS

An extracellular alkaline serine protease (Ds1) was purified and characterized from the nematode-trapping fungus D. shizishanna using cation-exchange chromatography and hydrophobic interaction chromatography. The molecular mass of the protease was approximately 35 kDa estimated by SDS-PAGE. The optimum activity of Ds1 was at pH 10 and 55 degrees C (over 30 min). The purified protease could degrade purified cuticle of Penagrellus redivivus and a broad range of protein substrates. The purified protease was highly sensitive to phenylmethyl sulfonyl fluoride (PMSF) (0.1 mmol l(-1)), indicating it belonged to the serine protease family. The N-terminal amino acid residues of Ds1 are AEQTDSTWGL and showed a high homology with Aozl and PII, two serine proteases purified from the nematode-trapping fungus Arthrobotrys oligospora.

CONCLUSIONS

Nematicidal activity of D. shizishanna was partly related to its ability to produce extracellular serine protease.

SIGNIFICANCE AND IMPACT OF THE STUDY

In this report, we purified a new serine protease from D. shizishanna and provided a good foundation for future research on infection mechanism.