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Arginine-to-lysine substitutions influence recombinant horseradish peroxidase stability and immobilisation effectiveness

Ryan, Barry J. and Ó'Fágáin, Ciarán (2007) Arginine-to-lysine substitutions influence recombinant horseradish peroxidase stability and immobilisation effectiveness. BMC Biotechnology, 7 (86). ISSN 1472-6750

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Abstract

Background: Horseradish Peroxidase (HRP) plays important roles in many biotechnological fields, including diagnostics, biosensors and biocatalysis. Often, it is used in immobilised form. With conventional immobilisation techniques, the enzyme adheres in random orientation: the active site may face the solid phase rather than bulk medium, impeding substrate access and leading to sub-optimal catalytic performance. The ability to immobilise HRP in a directional manner, such that the active site would always face outwards from the insoluble matrix, would maximise the immobilised enzyme’s catalytic potential and could increase HRP’s range of actual and potential applications. Results: We have replaced arginine residues on the face of glycan-free recombinant HRP opposite to the active site by lysines. Our strategy differs from previous reports of specific HRP immobilisation via an engineered affinity tag or single reactive residue. These conservative Arg-to-Lys substitutions provide a means of multipoint covalent immobilisation such that the active site will always face away from the immobilisation matrix. One triple and one pentuple mutant were generated by substitution of solvent-exposed arginines on the “back” of the polypeptide (R118, R159 and R283) and of residues known to influence stability (K232 and K241). Orientated HRP immobilisation was demonstrated using a modified polyethersulfone (PES) membrane; the protein was forced to orientate its active site away from the membrane and towards the bulk solution phase. Mutant properties and bioinformatic analysis suggested the reversion of K283R to improve stability, thus generating two additional mutants (K118/R159K and R118K/K232N/K241F/R283K). While most mutants were less stable in free solution than wild type rHRP, the quadruple revertant regained some stability over its mutant counterparts. A greater degree of immobilisation on CNBr-activated SepharoseTM was noted with increased lysine content; however, only marginal gains in solvent stability resulted from immobilisation on this latter matrix. Conclusions: Directional, orientated, immobilisation of rHRP mutants onto an activated, modified polyethersulfone membrane has been achieved with excellent retention of catalytic activity; however, re-engineering of acceptable stability characteristics into the “immobilisation mutants” will determine their applicability in diagnosis and biosensor development.

Item Type:Article (Published)
Refereed:Yes
Uncontrolled Keywords:Recombinant; Horseradish Peroxidase; Mutation; Directional Immobilisation;
Subjects:Biological Sciences > Biotechnology
Biological Sciences > Enzymology
DCU Faculties and Centres:DCU Faculties and Schools > Faculty of Science and Health > School of Biotechnology
Research Initiatives and Centres > National Centre for Sensor Research (NCSR)
Publisher:BioMed Central
Official URL:http://dx.doi.org/10.1186/1472-6750-7-86
Use License:This item is licensed under a Creative Commons Attribution-NonCommercial-Share Alike 3.0 License. View License
ID Code:113
Deposited On:09 Jan 2008 by DORAS Administrator. Last Modified 30 Jan 2009 16:06

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