Characterization of an extracellular serine protease of Fusarium eumartii and its action on pathogenesis related proteins

Abstract

Proteases have been proposed as part of the invasion strategies of some pathogenic fungi. In this work, a serine protease produced by the phytopathogenic fungus Fusarium solani f.sp. eumartii was purified and characterized. Purification of the enzyme was accomplished by gel filtration through a Superose 12 column, followed by hydrophobic interaction chromatography in Phenyl Superose and gel filtration chromatography through Superdex 75. Analysis of the purified enzyme by SDS/PAGE without heat treatment, revealed a single band, which corresponded to the proteolytic activity detected by zymogram. When this protein was subjected to denaturing conditions, two major polypeptides of approximately 30 and 33 kDa were revealed. The N-terminal amino acid sequence of one of these polypeptides showed a high similarity with fungal mature serine proteases of the subtilisin family. This protease hydrolysed in vitro, specific polypeptides of potato intercellular washing fluids and cell walls. The protease was also able to degrade pathogenesis-related proteins from the intercellular washing fluids. The role of this serine protease as part of the fungal strategy to colonize potato tuber tissues is discussed.