title: Aspergillus protein degradation pathways with different secreted protease sets at neutral and acidic pH.
abstract: Aspergillus fumigatus grows well at neutral and acidic pH in a medium containing protein as the sole nitrogen source by secreting two different sets of proteases. Neutral pH favors the secretion of neutral and alkaline endoproteases, leucine aminopeptidases (Laps) which are nonspecific monoaminopeptidases, and an X-prolyl dipeptidase (DppIV). Acidic pH environment promotes the secretion of an aspartic endoprotease of pepsin family (Pep1) and tripeptidyl-peptidases of the sedolisin family (SedB and SedD). A novel prolyl peptidase, AfuS28, was found to be secreted in both alkaline and acidic conditions. In previous studies, Laps were shown to degrade peptides from their N-terminus until an X-Pro sequence acts as a stop signal. X-Pro sequences can be then removed by DppIV, which allows Laps access to the following residues. We have shown that at acidic pH Seds degrade large peptides from their N-terminus into tripeptides until Pro in P1 or P'1 position acts as a stop for these exopeptidases. However, X-X-Pro and X-X-X-Pro sequences can be removed by AfuS28 thus allowing Seds further sequential proteolysis. In conclusion, both alkaline and acidic sets of proteases contain exoprotease activity capable of cleaving after proline residues that cannot be removed during sequential digestion by nonspecific exopeptidases.
authors.affiliation: Department of Dermatology, Centre Hospitalier Universitaire Vaudois, 1011 Lausanne, Switzerland.
authors.forename: Dev
authors.initials: D
authors.lastname: Sriranganadane
authors.forename: Patrice
authors.initials: P
authors.lastname: Waridel
authors.forename: Karine
authors.initials: K
authors.lastname: Salamin
authors.forename: Utz
authors.initials: U
authors.lastname: Reichard
authors.forename: Eric
authors.initials: E
authors.lastname: Grouzmann
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Neuhaus
authors.forename: Manfredo
authors.initials: M
authors.lastname: Quadroni
authors.forename: Michel
authors.initials: M
authors.lastname: Monod
mesh_terms: D000595:Amino Acid Sequence; D001230:Aspergillus / Q000201:enzymology* / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D005656:Fungal Proteins / Q000737:chemistry / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000378:metabolism*; D010447:Peptide Hydrolases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D005656:Fungal Proteins; D010446:Peptide Fragments; D010447:Peptide Hydrolases