Improving the pH-stability of Versatile Peroxidase by Comparative Structural Analysis with a Naturally-Stable Manganese Peroxidase

PLoS One. 2015 Oct 23;10(10):e0140984. doi: 10.1371/journal.pone.0140984. eCollection 2015.

Abstract

Versatile peroxidase (VP) from the white-rot fungus Pleurotus eryngii is a high redox potential peroxidase of biotechnological interest able to oxidize a wide range of recalcitrant substrates including lignin, phenolic and non-phenolic aromatic compounds and dyes. However, the relatively low stability towards pH of this and other fungal peroxidases is a drawback for their industrial application. A strategy based on the comparative analysis of the crystal structures of VP and the highly pH-stable manganese peroxidase (MnP4) from Pleurotus ostreatus was followed to improve the VP pH stability. Several interactions, including hydrogen bonds and salt bridges, and charged residues exposed to the solvent were identified as putatively contributing to the pH stability of MnP4. The eight amino acid residues responsible for these interactions and seven surface basic residues were introduced into VP by directed mutagenesis. Furthermore, two cysteines were also included to explore the effect of an extra disulfide bond stabilizing the distal Ca2+ region. Three of the four designed variants were crystallized and new interactions were confirmed, being correlated with the observed improvement in pH stability. The extra hydrogen bonds and salt bridges stabilized the heme pocket at acidic and neutral pH as revealed by UV-visible spectroscopy. They led to a VP variant that retained a significant percentage of the initial activity at both pH 3.5 (61% after 24 h) and pH 7 (55% after 120 h) compared with the native enzyme, which was almost completely inactivated. The introduction of extra solvent-exposed basic residues and an additional disulfide bond into the above variant further improved the stability at acidic pH (85% residual activity at pH 3.5 after 24 h when introduced separately, and 64% at pH 3 when introduced together). The analysis of the results provides a rational explanation to the pH stability improvement achieved.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Crystallography, X-Ray
  • Enzyme Stability
  • Fungal Proteins / chemistry
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism
  • Hydrogen-Ion Concentration
  • Peroxidase / chemistry*
  • Peroxidase / genetics
  • Peroxidase / metabolism*
  • Peroxidases / chemistry*
  • Peroxidases / genetics
  • Peroxidases / metabolism*
  • Pleurotus / chemistry
  • Pleurotus / genetics
  • Pleurotus / metabolism

Substances

  • Fungal Proteins
  • Peroxidases
  • manganese peroxidase
  • Peroxidase

Associated data

  • PDB/5ABN
  • PDB/5ABO
  • PDB/5ABQ

Grants and funding

“Novel and more robust fungal peroxidases as industrial biocatalysts”) and INDOX (KBBE-2013-7-613549, “Optimized oxidoreductases for medium and large scale industrial biotransformations”) projects to ATM, by the Spanish Ministerio de Economía y Competitividad (MINECO) through the HIPOP (BIO2011-26694, “Screening and engineering of new high-redoxpotential peroxidases”) to FJR-D, NOESIS (BIO-2014-56388-R, “New oxidative enzymes for sustainable industries”) to FJR-D, BFU2011-24615 and CSD2009-00088 projects, and by the EC 7th Framework Programme (FP7/2007-2013) under BioStructx-5959 (grant agreement N° 283570). VS-J and FJR-D thank the financial support of a research fellowship (Formación de Personal Investigador, FPI) and a Ramón y Cajal contract of the Spanish MINECO, respectively. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.