Identification and Characterization of a Novel Galactofuranose-Specific β-D-Galactofuranosidase from Streptomyces Species

PLoS One. 2015 Sep 4;10(9):e0137230. doi: 10.1371/journal.pone.0137230. eCollection 2015.

Abstract

β-D-galactofuranose (Galf) is a component of polysaccharides and glycoconjugates and its transferase has been well analyzed. However, no β-D-galactofuranosidase (Galf-ase) gene has been identified in any organism. To search for a Galf-ase gene we screened soil samples and discovered a strain, identified as a Streptomyces species by the 16S ribosomal RNA gene analysis, that exhibits Galf-ase activity for 4-nitrophenyl β-D-galactofuranoside (pNP-β-D-Galf) in culture supernatants. By draft genome sequencing of the strain, named JHA19, we found four candidate genes encoding Galf-ases. Using recombinant proteins expressed in Escherichia coli, we found that three out of four candidates displayed the activity of not only Galf-ase but also α-L-arabinofuranosidase (Araf-ase), whereas the other one showed only the Galf-ase activity. This novel Galf-specific hydrolase is encoded by ORF1110 and has an optimum pH of 5.5 and a Km of 4.4 mM for the substrate pNP-β-D-Galf. In addition, this enzyme was able to release galactose residue from galactomannan prepared from the filamentous fungus Aspergillus fumigatus, suggesting that natural polysaccharides could be also substrates. By the BLAST search using the amino acid sequence of ORF1110 Galf-ase, we found that there are homolog genes in both prokaryotes and eukaryotes, indicating that Galf-specific Galf-ases widely exist in microorganisms.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Aspergillus fumigatus / genetics
  • Aspergillus fumigatus / metabolism
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Cloning, Molecular
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Galactose / analogs & derivatives
  • Galactose / metabolism*
  • Genome, Bacterial*
  • Glycoconjugates / chemistry
  • Glycoconjugates / metabolism
  • Glycoside Hydrolases / genetics
  • Glycoside Hydrolases / metabolism*
  • High-Throughput Nucleotide Sequencing
  • Hydrogen-Ion Concentration
  • Kinetics
  • Mannans / chemistry
  • Mannans / isolation & purification
  • Molecular Sequence Data
  • Open Reading Frames
  • Phylogeny
  • RNA, Ribosomal, 16S / genetics
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Sequence Alignment
  • Sequence Homology, Amino Acid
  • Streptomyces / enzymology*
  • Streptomyces / genetics
  • Substrate Specificity

Substances

  • Bacterial Proteins
  • Glycoconjugates
  • Mannans
  • RNA, Ribosomal, 16S
  • Recombinant Proteins
  • galactomannan
  • Glycoside Hydrolases
  • exo-beta-D-galactofuranosidase
  • Galactose

Grants and funding

This work was supported by JSPS KAKENHI (https://www.jsps.go.jp/english/index.html) Grant Numbers 26292054 to K. Takegawa and 26892022 to YH. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.