期刊
PLOS ONE
卷 7, 期 6, 页码 -出版社
PUBLIC LIBRARY SCIENCE
DOI: 10.1371/journal.pone.0038134
关键词
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资金
- Spanish CDTI [CENIT 2007-1031]
- Ministry of Economy and Competitiveness
- Spanish MEC
- CSIC
- Federal Ministry for Science and Education (BMBF) within the GenoMikPlus initiative [0313751K]
Microbial communities from cow rumen are known for their ability to degrade diverse plant polymers at high rates. In this work, we identified 15 hydrolases through an activity-centred metagenome analysis of a fibre-adherent microbial community from dairy cow rumen. Among them, 7 glycosyl hydrolases (GHs) and 1 feruloyl esterase were successfully cloned, expressed, purified and characterised. The most striking result was a protein of GH family 43 (GHF43), hereinafter designated as R_09-02, which had characteristics very distinct from the other proteins in this family with mono-functional beta-xylosidase, alpha-xylanase, alpha-L-arabinase and alpha-L-arabinofuranosidase activities. R_09-02 is the first multifunctional enzyme to exhibit beta-1,4 xylosidase, alpha-1,5 arabinofur(pyr)anosidase, beta-1,4 lactase, alpha-1,6 raffinase, alpha-1,6 stachyase, alpha-galactosidase and alpha-1,4 glucosidase activities. The R_09-02 protein appears to originate from the chromosome of a member of Clostridia, a class of phylum Firmicutes, members of which are highly abundant in ruminal environment. The evolution of R_09-02 is suggested to be driven from the xylose-and arabinose-specific activities, typical for GHF43 members, toward a broader specificity to the glucose-and galactose-containing components of lignocellulose. The apparent capability of enzymes from the GHF43 family to utilise xylose-, arabinose-, glucose-and galactose-containing oligosaccharides has thus far been neglected by, or could not be predicted from, genome and metagenome sequencing data analyses. Taking into account the abundance of GHF43-encoding gene sequences in the rumen (up to 7% of all GH-genes) and the multifunctional phenotype herein described, our findings suggest that the ecological role of this GH family in the digestion of ligno-cellulosic matter should be significantly reconsidered.
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