Related Experiment Video
Updated: Feb 22, 2026
Single-Step Enrichment of a TAP-Tagged Histone Deacetylase of the Filamentous Fungus Aspergillus nidulans for Enzymatic Activity Assay
Published on: May 1, 2019
Trichosporon asahii secretes a 30-kDa aspartic peptidase
Roberta S Valle1, Lívia S Ramos1, Vanessa J Reis1
1Laboratório de Investigação de Peptidases, Departamento de Microbiologia Geral, Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.
Abstract:
Trichosporon asahii is a fungal opportunistic pathogen that causes superficial and deep-seated infections presenting high mortality. Very little is known about the virulence attributes produced by this fungus. Herein, aspartic peptidase production was identified in Brazilian clinical isolates of T. asahii by different methodologies. Initially, T. asahii strain 250 (from skin lesion) was inoculated in both liquid and solid culture media containing bovine serum albumin (BSA) as the sole nitrogenous source. A translucent halo around the fungal colony was observed from the 5th day of culture. The cell-free culture supernatant revealed that soluble BSA was hydrolyzed along the growth, generating low molecular mass polypeptides as observed by electrophoresis. Subsequently, the secretions from four clinical strains of T. asahii were analyzed by BSA-SDS-PAGE and a single proteolytic band of 30-kDa was detected under acidic pH at 37°C. The secreted aspartic peptidase of T. asahii efficiently cleaved the cathepsin D peptide substrate, but not the substrates with specificity to HIV-1 peptidase and rennin. The capability to cleave either cathepsin D substrate in a fluorogenic assay or BSA immobilized within a gel matrix varied according to the T. asahii isolate. T. asahii extracellular peptidase activity was strongly inhibited by pepstatin A and HIV peptidase inhibitors, classifying it as an aspartic-type peptidase. Human serum albumin, mucin, non-immune immunoglobulin G and gelatin induced, in different levels, the secretion of this aspartic peptidase. With these results, T. asahii must be included in the list of many human fungal opportunistic pathogens able to secrete an aspartic-type peptidase.
Insights
Brazilian clinical isolates of Trichosporon asahii produce an aspartic peptidase. This enzyme aids in fungal virulence and can be induced by host proteins, highlighting its role in opportunistic infections.
Area of Science:
- Medical Mycology
- Molecular Pathogenesis
- Biochemistry
Background:
- Trichosporon asahii is an opportunistic fungal pathogen causing severe infections with high mortality.
- The virulence factors of T. asahii remain largely uncharacterized.
- Understanding fungal secreted enzymes is crucial for developing targeted therapies.
Purpose of the Study:
- To identify and characterize aspartic peptidase production in clinical isolates of T. asahii.
- To investigate the enzymatic activity and substrate specificity of the secreted peptidase.
- To determine factors that induce the secretion of this enzyme.
Main Methods:
- Culturing T. asahii clinical isolates with bovine serum albumin (BSA) as a nitrogen source.
- Analyzing secreted proteins using BSA-SDS-PAGE to detect proteolytic activity.
- Assessing peptidase activity using specific peptide substrates and fluorogenic assays.
- Testing the effect of pepstatin A and HIV peptidase inhibitors on enzyme activity.
- Evaluating the induction of peptidase secretion by host-derived proteins.
Main Results:
- Brazilian clinical isolates of T. asahii secrete an aspartic peptidase, with a 30-kDa band detected under acidic conditions.
- The enzyme efficiently cleaved cathepsin D substrates but not those specific for HIV-1 peptidase or rennin.
- Enzyme activity was inhibited by pepstatin A and HIV peptidase inhibitors, confirming its aspartic type.
- Secretion of the aspartic peptidase was induced by human serum albumin, mucin, immunoglobulin G, and gelatin.
- The ability to cleave substrates varied among different T. asahii isolates.
Conclusions:
- T. asahii clinical isolates possess the capability to secrete an aspartic-type peptidase.
- This secreted peptidase is a potential virulence factor contributing to T. asahii pathogenesis.
- The induction of peptidase secretion by host proteins suggests a mechanism for fungal adaptation and invasion.
- T. asahii should be recognized as a fungal pathogen secreting aspartic peptidases, similar to other opportunistic fungi.
Related Concept Videos
01:28Fungal Phylum Ascomycota
01:24Caspases
01:28Fungal Phylum Microsporidia
01:28Protein Translocation Machinery on the ER Membrane
Sec61 protein conducting channel
In eukaryotes, the translocon complex comprises a core heterotrimeric translocator channel called the Sec61 complex. This channel includes three transmembrane proteins, Sec61α, Sec61β, and Sec61γ, and is the largest subunit of the...
02:18The Proteasome
In this pathway, the target proteins are first tagged with small proteins called ubiquitin. A series of enzymes carry out the ubiquitination of the target proteins - E1 (ubiquitin-activating enzyme), E2 (ubiquitin-conjugating enzyme), and E3...
01:24Protein Transport to the Stroma
Protein complexes called the translocon of the outer chloroplast membrane or TOC complex, and the translocon of the inner chloroplast membrane or TIC complex mediate the...