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Sedolisins, a New Class of Secreted Proteases from Aspergillus fumigatus with Endoprotease or Tripeptidyl-Peptidase Activity at Acidic pHs

Author:
Reichard, Utz, Léchenne, Barbara, Asif, Abdul R., Streit, Frank, Grouzmann, Eric, Jousson, Olivier, Monod, Michel
Source:
Applied and environmental microbiology 2006 v.72 no.3 pp. 1739-1748
ISSN:
0099-2240
Subject:
Aspergillus fumigatus, Merops, Pichia pastoris, Western blotting, enzyme activity, genes, hemoglobin, hydrolysis, nitrogen, pH, protein sources, proteinases, signal peptide, substrate specificity, virulence
Abstract:
The secreted proteolytic activity of Aspergillus fumigatus is of potential importance as a virulence factor and in the industrial hydrolysis of protein sources. The A. fumigatus genome contains sequences that could encode a five-member gene family that produces proteases in the sedolisin family (MEROPS S53). Four putative secreted sedolisins with a predicted 17- to 20-amino-acid signal sequence were identified and termed SedA to SedD. SedA produced heterologously in Pichia pastoris was an acidic endoprotease. Heterologously produced SedB, SedC, and SedD were tripeptidyl-peptidases (TPP) with a common specificity for tripeptide-p-nitroanilide substrates at acidic pHs. Purified SedB hydrolyzed the peptide Ala-Pro-Gly-Asp-Arg-Ile-Tyr-Val-His-Pro-Phe to Arg-Pro-Gly, Asp-Arg-Ile, and Tyr-Val-His-Pro-Phe, thereby confirming TPP activity of the enzyme. SedB, SedC, and SedD were detected by Western blotting in culture supernatants of A. fumigatus grown in a medium containing hemoglobin as the sole nitrogen source. A degradation product of SedA also was observed. A search for genes encoding sedolisin homologues in other fungal genomes indicates that sedolisin gene families are widespread among filamentous ascomycetes.
Agid:
574545