Structure and function of an acetyl xylan esterase (Est2A) from the rumen bacterium Butyrivibrio proteoclasticus

Proteins. 2013 May;81(5):911-7. doi: 10.1002/prot.24254. Epub 2013 Feb 25.


Butyrivibrio proteoclasticus is a significant component of the microbial population of the rumen of dairy cattle. It is a xylan-degrading organism whose genome encodes a large number of open reading frames annotated as fiber-degrading enzymes. We have determined the three-dimensional structure of Est2A, an acetyl xylan esterase from B. proteoclasticus, at 2.1 Å resolution, along with the structure of an inactive mutant (H351A) at 2.0 Å resolution. The structure reveals two domains-a C-terminal SGNH domain and an N-terminal jelly-roll domain typical of CE2 family structures. The structures are accompanied by experimentally determined enzymatic parameters against two model substrates, para-nitrophenyl acetate and para-nitrophenyl butyrate. The suite of fiber-degrading enzymes produced by B. proteoclasticus provides a rich source of new enzymes of potential use in industrial settings.

MeSH terms

  • Acetylesterase / chemistry*
  • Acetylesterase / genetics
  • Acetylesterase / metabolism*
  • Animals
  • Butyrivibrio / enzymology*
  • Butyrivibrio / genetics
  • Butyrivibrio / metabolism
  • Cattle / microbiology*
  • Cellulose / metabolism
  • Crystallography, X-Ray
  • Models, Molecular
  • Mutagenesis, Site-Directed
  • Mutation
  • Protein Conformation


  • Cellulose
  • Acetylesterase
  • acetylxylan esterase