Effects of mutations in the helix G region of horseradish peroxidase.
Horseradish peroxidase (HRP) has long attracted intense research interest and is used in many biotechnological fields, including diagnostics, biosensors and biocatalysis. Enhancement of HRP catalytic activity and/or stability would further increase its usefulness. Based on prior art, we substituted solvent-exposed lysine and glutamic acid residues near the proximal helix G (Lys 232, 241; Glu 238, 239) and between helices F and F' (Lys 174). Three single mutants (K232N, K232F, K241N) demonstrated increased stabilities against heat (up to 2-fold) and solvents (up to 4-fold). Stability gains are likely due to improved hydrogen bonding and space-fill characteristics introduced by the relevant substitution. Two double mutants showed stability gains but most double mutations were non-additive and non-synergistic. Substitutions of Lys 174 or Glu 238 were destabilising. Unexpectedly, notable alterations in steady-state Vm/E values occurred with reducing substrate ABTS (2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid)), despite the distance of the mutated positions from the active site.
School of Biotechnology and National Centre for Sensors Research, Dublin City University, Dublin 9, Ireland.
Barry J
BJ
Ryan
Ciarán
C
O'Fágáin
D002118:Calcium / Q000737:chemistry / Q000378:metabolism; D004795:Enzyme Stability; D006735:Horseradish Peroxidase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006860:Hydrogen Bonding; D009154:Mutation / Q000235:genetics; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D013696:Temperature
D011994:Recombinant Proteins; D006735:Horseradish Peroxidase; D002118:Calcium