Directed evolution of a temperature-, peroxide- and alkaline pH-tolerant versatile peroxidase

Biochem J. 2012 Jan 1;441(1):487-98. doi: 10.1042/BJ20111199.

Abstract

The VPs (versatile peroxidases) secreted by white-rot fungi are involved in the natural decay of lignin. In the present study, a fusion gene containing the VP from Pleurotus eryngii was subjected to six rounds of directed evolution, achieving a level of secretion in Saccharomyces cerevisiae (21 mg/l) as yet unseen for any ligninolytic peroxidase. The evolved variant for expression harboured four mutations and increased its total VP activity 129-fold. The signal leader processing by the STE13 protease at the Golgi compartment changed as a consequence of overexpression, retaining the additional N-terminal sequence Glu-Ala-Glu-Ala that enhanced secretion. The engineered N-terminally truncated variant displayed similar biochemical properties to those of the non-truncated counterpart in terms of kinetics, stability and spectroscopic features. Additional cycles of evolution raised the T50 8°C and significantly increased the enzyme's stability at alkaline pHs. In addition, the Km for H2O2 was enhanced up to 15-fold while the catalytic efficiency was maintained, and there was an improvement in peroxide stability (with half-lives for H2O2 of 43 min at a H2O2/enzyme molar ratio of 4000:1). Overall, the directed evolution approach described provides a set of strategies for selecting VPs with improvements in secretion, activity and stability.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Binding Sites
  • Directed Molecular Evolution
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism*
  • Gene Expression Regulation, Fungal / physiology
  • Hydrogen Peroxide / pharmacology*
  • Hydrogen-Ion Concentration
  • Manganese / metabolism
  • Models, Molecular
  • Peroxidases / classification
  • Peroxidases / genetics
  • Peroxidases / metabolism*
  • Pleurotus / genetics
  • Pleurotus / metabolism*
  • Protein Binding
  • Protein Conformation
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism*
  • Temperature*

Substances

  • Fungal Proteins
  • Manganese
  • Hydrogen Peroxide
  • Peroxidases