title: Isolation of four pepsin-like protease genes from Aspergillus niger and analysis of the effect of disruptions on heterologous laccase expression.
abstract: Four new aspartic protease genes pepAa, pepAb, pepAc and pepAd from Aspergillus niger were identified using a comparative genomic approach. All four gene products have highly conserved attributes that are characteristic of aspartic proteases; however, each one has novel sequence features. The PEPAa protease appears to represent an ortholog of a pepsin-type aspartic protease previously identified from Talaromyces emersonii and Scleotinia sclerotiorum. The PEPAb protease appears to be an ortholog of an aspartic protease previously identified from BcAP1 of Botryotinia fuckeliana. The PEPAc protease also appears to be an ortholog of BcAP5 from B. fuckeliana. These four genes appear to be conserved in many species of filamentous fungi, all except PEPAb contain a predicted signal peptide. Transcriptome analysis revealed that transcripts of the pepAa gene of Aspergillus nidulans were significantly up-regulated due to recombinant chymosin secretion, suggesting that silencing these genes may lead to improved yields of secreted proteins. To establish the effects of reduced protease activity on the stabilities of secreted proteins, three of the four genes were individually disrupted by double crossover, although we were unable to disrupt the pepAc gene. The secretion level of heterologous laccase in the pepAa, pepAb and pepAd disruption mutants were increased by about 21%, 42% and 30%, respectively. And their total glucogenic enzymes secretion were also increased by about 18.7%, 37.0% and 5.20%, respectively.
authors.affiliation: Key Laboratory of Systematic Mycology and Lichenology, Institute of Microbiology, Chinese Academy of Sciences, 100101 Beijing, PR China.
authors.forename: Yongchao
authors.initials: Y
authors.lastname: Wang
authors.forename: Wei
authors.initials: W
authors.lastname: Xue
authors.forename: Andrew H
authors.initials: AH
authors.lastname: Sims
authors.forename: Chuntian
authors.initials: C
authors.lastname: Zhao
authors.forename: Aoquan
authors.initials: A
authors.lastname: Wang
authors.forename: Guomin
authors.initials: G
authors.lastname: Tang
authors.forename: Junchuan
authors.initials: J
authors.lastname: Qin
authors.forename: Huaming
authors.initials: H
authors.lastname: Wang
mesh_terms: D000595:Amino Acid Sequence; D016282:Aspartic Acid Endopeptidases / Q000235:genetics*; D001234:Aspergillus niger / Q000201:enzymology / Q000235:genetics*; D015536:Down-Regulation; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism*; D017353:Gene Deletion; D042845:Laccase / Q000378:metabolism*; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000235:genetics; D010434:Pepsin A; D016415:Sequence Alignment
chemical_list: D005656:Fungal Proteins; D042845:Laccase; D016282:Aspartic Acid Endopeptidases; D010434:Pepsin A