Crystal structure of a novel xylose isomerase from Streptomyces sp. F-1 revealed the presence of unique features that differ from conventional classes

Biochim Biophys Acta Gen Subj. 2020 May;1864(5):129549. doi: 10.1016/j.bbagen.2020.129549. Epub 2020 Feb 5.

Abstract

Background: Enzymatic isomerization is a promising strategy to solve the problem of xylose fermentation and, consequently, to leverage the production of advanced biofuels and biochemicals. In a previous work, our research group discovered a new strain of Streptomyces with great biotechnological potential due to its ability to produce a broad arsenal of enzymes related to lignocellulose degradation.

Methods: We applied a multidisciplinary approach involving enzyme kinetics, biophysical methods, small angle X-ray scattering and X-ray crystallography to investigate two novel xylose isomerases, XylA1F1 and XylA2F1, from this strain.

Results: We showed that while XylA1F1 prefers to act at lower temperatures and relatively lower pH, XylA2F1 is extremely stable at higher temperatures and presents a higher turnover number. Structural analysis revealed that XylA1F1 exhibits unique properties in the active site not observed in classical XylAs from classes I and II nor in its ortholog XylA2F1. It encompasses the natural substitutions, M86A and T93K, that create an extra room for substrate accommodation and narrow the active-site entrance, respectively. Such modifications may contribute to the functional differentiation of these enzymes.

Conclusions: We have characterized two novel xylose isomerases that display distinct functional behavior and harbor unprecedented amino-acid substitutions in the catalytic interface.

General significance: Our findings contribute to a better understanding of the functional and structural aspects of xylose isomerases, which might be instrumental for the valorization of the hemicellulosic fraction of vegetal biomass.

Keywords: Biofuels; Crystal structure; Enzyme kinetics; Hemicellulosic fraction; Structure-function relationship; Xylose isomerase.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aldose-Ketose Isomerases / chemistry*
  • Aldose-Ketose Isomerases / metabolism
  • Amino Acid Sequence
  • Catalytic Domain
  • Crystallography, X-Ray
  • Models, Molecular
  • Protein Conformation
  • Sequence Alignment
  • Streptomyces / chemistry
  • Streptomyces / enzymology*
  • Streptomyces / metabolism
  • Substrate Specificity

Substances

  • Aldose-Ketose Isomerases
  • xylose isomerase