The role of tryptophan residues in radiation sensitivity of enzymes as exemplified in horseradish peroxidase |
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Authors: | T A Chubar' M A Orlova I G Gazaryan V A Fechina E A Mareeva O V Ignatenko P A Savitskii A M Rozhkova V I Tishkov |
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Institution: | (1) Department of Chemistry, M. V. Lomonosov Moscow State University, Leninskie Gory, 119899 Moscow, Russian Federation |
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Abstract: | The stability of recombinant wild-type horseradish peroxidase and its tryptophan-less mutant Trp117Phe toward γ-radiation
was studied. The absence of tryptophan in the enzyme molecule results in a certain stabilization, which is manifested as the
absence of the initial drop in activity and appearance of a lag period for doses of up to 45 Gy. Contrary to the wild-type
enzyme, the dose response of the mutant is almost independent of the nature of the substrate used to measure the catalytic
activity; this indirectly indicates that Trp117 participates in the oxidation of substrates. Pretreatment of the wild-type
recombinant enzyme with hydrogen peroxide destabilizes the enzyme towards irradiation, while the same procedure for the mutant
enzyme has virtually no effect on the dose response curve. This suggests the modification of Trp117 in the oxidation of the
native enzyme with H2O2 in the absence of electron-donor substrates, which is the modification of Trp171 in the recombinant lignin peroxidase.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2355–2358, December, 1999. |
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Keywords: | radiation-induced inactivation recombinant horseradish peroxidase mutagenesis Trp117Phe modification hydrogen peroxide |
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