Substrate recognition and hydrolysis by a fungal xyloglucan-specific family 12 hydrolase

Carbohydr Res. 2009 Jul 6;344(10):1175-9. doi: 10.1016/j.carres.2009.04.020. Epub 2009 Apr 22.

Abstract

Biochemical studies to elucidate the structural basis for xyloglucan specificity among GH12 xyloglucanases are lacking. Accordingly, the substrate specificity of a GH12 xyloglucanase from Aspergillus niger (AnXEG12A) was investigated using pea xyloglucan and 12 xylogluco-oligosaccharides, and data were compared to a structural model of the enzyme. The specific activity of AnXEG12A with pea xyloglucan was 113 micromol min(-1)mg(-1), and apparent k(cat) and K(m) values were 49 s(-1) and 0.54 mg mL(-1), respectively. These values are similar to previously published results using xyloglucan from tamarind seed, and suggest that substrate fucosylation does not affect the specific activity of this enzyme. AnXEG12A preferred xylogluco-oligosaccharides containing more than six glucose units, and with xylose substitution at the -3 and +1 subsites. The specific activities of AnXEG12A on 100 microM XXXGXXXG and 100 microM XLLGXLLG were 60+/-4 and 72+/-9 micromol min(-1)mg(-1), respectively. AnXEG12A did not hydrolyze XXXXXXXG, consistent with other data that demonstrate the requirement for an unbranched glucose residue for hydrolysis by this enzyme.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aspergillus niger / enzymology*
  • Carbohydrate Sequence
  • Glucans / chemistry
  • Glucans / metabolism*
  • Glycoside Hydrolases / chemistry
  • Glycoside Hydrolases / metabolism*
  • Hydrolysis
  • Models, Molecular
  • Molecular Sequence Data
  • Peas / chemistry
  • Protein Conformation
  • Substrate Specificity
  • Xylans / chemistry
  • Xylans / metabolism*

Substances

  • Glucans
  • Xylans
  • xyloglucan
  • Glycoside Hydrolases
  • xyloglucan endo(1-4)-beta-D-glucanase