Kinetic studies on the oxidation of nitrite by horseradish peroxidase and lactoperoxidase

• Authors: Lidia Gębicka
• Languages of publication: EN

Abstracts

EN

The reaction of nitrite (NO-_2) with horseradish peroxidase and lactoperoxidase was studied. Sequential mixing sopped-flow measeruments gave the following values for the rate constants of the reaction of nitrite with compounds II (oxoferryl heme intermediates) of horseradish peroxidase and lactoperoxidase at pH 7.0, 13.3 ± 0.07 mol^{-1}dm^3s^{-1} and 3.5 ± 0.05 · 10^4mol^{-1}dm^3s^{-1}, respectively. Nitrite, at neutral pH, influenced measurements of activity of lactoperoxidase with typical substrates like 2,2'-azino-bis[ethyl-benzothiazoline-(6)-sulphonic acid] (ABTS), guaiacol or thiocyanate (SCN-). The rate of ABTS and guaiacol oxidation increased linearly with nitrite concentration up to 2.5-5 mmol dm^{-3}. On the other hand, two-electron SCN- oxidation was inhibited in the presence od nitrite. Thus, nitrite competed with the investigated substrates of lactoperoxidase. The intermediate, most probably nitrogen dioxide (*NO_2), reacted more rapidly with ABTS or guaiacol than did lactoperoxidase compound II. It did not, however, effectively oxidize SCN- to OSCN-. NO-_2 did not influence the activity measurements of horseradish peroxidase by ABTS or guaiacol method.

Keywords

EN

lactoperoxidase; nitrite; stopped-flow; horseradish peroxidase

• Publisher: Polish Biochemical Society
• Journal: Acta Biochimica Polonica
• Year: 1999
• Volume: 46
• Issue: 4
• Pages: 919-927

Dates

published

1999

received

1999-10-14

Contributors

author

Lidia Gębicka

• Institute of Applied Radiation Chemistry, Technical University of Łódź, W. Wróblewskiego 15, 93-950 Łódź