Catalase-peroxidases are bifunctional peroxidases exhibiting an overwhelming catalase activity and a substantial peroxidase activity. Here we present a kinetic study of the formation and reduction of the key intermediate compound I by probing the role of the conserved tryptophan at the distal haem cavity site. Two wild-type proteins and three mutants of Synechocystis catalase-peroxidase (W122A and W122F) and Escherichia coli catalase-peroxidase (W105F) have been investigated by steady-state and stopped-flow spectroscopy. W122F and W122A completely lost their catalase activity whereas in W105F the catalase activity was reduced by a factor of about 5000. However, the mutations did not influence both formation of compound I and its reduction by peroxidase substrates. It was demonstrated unequivocally that the rate of compound I reduction by pyrogallol or o-dianisidine sometimes even exceeded that of the wild-type enzyme. This study demonstrates that the indole ring of distal Trp in catalase-peroxidases is essential for the two-electron reduction of compound I by hydrogen peroxide but not for compound I formation or for peroxidase reactivity (i.e. the one-electron reduction of compound I).
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May 01 2001
The role of distal tryptophan in the bifunctional activity of catalase-peroxidases Available to Purchase
G. Regelsberger;
G. Regelsberger
*Institute of Chemistry, University of Agricultural Sciences, Muthgasse 18, A-1190 Vienna, Austria
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C. Jakopitsch;
C. Jakopitsch
*Institute of Chemistry, University of Agricultural Sciences, Muthgasse 18, A-1190 Vienna, Austria
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P. G. Furtmüller;
P. G. Furtmüller
*Institute of Chemistry, University of Agricultural Sciences, Muthgasse 18, A-1190 Vienna, Austria
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F. Rueker;
F. Rueker
†Institute of Applied Microbiology, University of Agricultural Sciences, Muthgasse 18, A-1190 Vienna, Austria
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J. Switala;
J. Switala
‡Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
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P. C. Loewen;
P. C. Loewen
‡Department of Microbiology, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
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C. Obinger
C. Obinger
1
*Institute of Chemistry, University of Agricultural Sciences, Muthgasse 18, A-1190 Vienna, Austria
1To whom correspondence should be addressed (e-mail [email protected])
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Publisher: Portland Press Ltd
Received:
October 25 2000
Online ISSN: 1470-8752
Print ISSN: 0300-5127
© 2001 Biochemical Society
2001
Biochem Soc Trans (2001) 29 (2): 99–105.
Article history
Received:
October 25 2000
Citation
G. Regelsberger, C. Jakopitsch, P. G. Furtmüller, F. Rueker, J. Switala, P. C. Loewen, C. Obinger; The role of distal tryptophan in the bifunctional activity of catalase-peroxidases. Biochem Soc Trans 1 May 2001; 29 (2): 99–105. doi: https://doi.org/10.1042/bst0290099
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