The Immunoreactive Exo-1,3-β-Glucanase from the Pathogenic Oomycete Pythium insidiosum Is Temperature Regulated and Exhibits Glycoside Hydrolase Activity

PLoS One. 2015 Aug 11;10(8):e0135239. doi: 10.1371/journal.pone.0135239. eCollection 2015.


The oomycete organism, Pythium insidiosum, is the etiologic agent of the life-threatening infectious disease called "pythiosis". Diagnosis and treatment of pythiosis is difficult and challenging. Novel methods for early diagnosis and effective treatment are urgently needed. Recently, we reported a 74-kDa immunodominant protein of P. insidiosum, which could be a diagnostic target, vaccine candidate, and virulence factor. The protein was identified as a putative exo-1,3-ß-glucanase (Exo1). This study reports on genetic, immunological, and biochemical characteristics of Exo1. The full-length exo1 coding sequence (2,229 bases) was cloned. Phylogenetic analysis showed that exo1 is grouped with glucanase-encoding genes of other oomycetes, and is far different from glucanase-encoding genes of fungi. exo1 was up-regulated upon exposure to body temperature, and its gene product is predicted to contain BglC and X8 domains, which are involved in carbohydrate transport, binding, and metabolism. Based on its sequence, Exo1 belongs to the Glycoside Hydrolase family 5 (GH5). Exo1, expressed in E. coli, exhibited ß-glucanase and cellulase activities. Exo1 is a major intracellular immunoreactive protein that can trigger host immune responses during infection. Since GH5 enzyme-encoding genes are not present in human genomes, Exo1 could be a useful target for drug and vaccine development against this pathogen.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antigens / genetics
  • Antigens / immunology
  • Antigens / metabolism
  • Enzyme Activation
  • Gene Expression
  • Glucan 1,3-beta-Glucosidase / genetics
  • Glucan 1,3-beta-Glucosidase / immunology
  • Glucan 1,3-beta-Glucosidase / metabolism*
  • Glycoside Hydrolases / metabolism
  • Hydrolysis
  • Molecular Sequence Data
  • Peptide Fragments / immunology
  • Peptide Fragments / metabolism
  • Phylogeny
  • Pythium / genetics
  • Pythium / immunology
  • Pythium / metabolism*
  • Temperature*
  • Transcription, Genetic


  • Antigens
  • Peptide Fragments
  • Glycoside Hydrolases
  • Glucan 1,3-beta-Glucosidase

Associated data

  • GENBANK/LC033486
  • GENBANK/LC033487
  • GENBANK/LC033488
  • GENBANK/LC033489
  • GENBANK/LC033490
  • GENBANK/LC033491

Grants and funding

This work is supported by the Thailand Research Fund (TKr; Grant number, RMU5380047; URL,, a Research Fund from Mahidol University (TKr; Grant number, E01/2557; URL,, and the Royal Golden Jubilee Ph.D. Scholarship (AK; Grant number, PHD/0199/2551; URL, The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.