Based on literature; Activity measurement of laccase and mangenese peroxidase (MnP) can be done using a same substrate (ABTS or DMP). the difference is that MnP need cofactors (mediators) for its activity, which are Mn2+ and H2O2, but laccase don't need these mediators. Therefore, measurement will be done without the mediators for laccase, and another time with mediators for laccase and MnP. The difference of these two measurements is MnP activity.
But when i tried to test these protocols i observed that when i added the mediators, enzyme activity was less than when i didn't add them. Note that i used same concentrations of same stock enzyme solutions.
Laccase activity seems to be sensitive to the amount of hydrogen peroxide, and even Manganese peroxidase even though it's a peroxidase an excessive amount of hydrogen peroxide might also inhibit its activity. Answering your main question, you might check the attached article or you might also try to measure MnP activity in a different way: https://www.researchgate.net/post/How_I_can_differentiate_between_the_activity_of_Laccase_and_Mn_Peroxidase?pli=1&loginT=ukSWMS-0BTFq9145V1SYiAjzFkhgxX8Gm-_BxNvHIHslbG54T9u_UQ&uid=8758b2a9-458f-4bcc-91ef-7c6fde78ee11&cp=re221_sk_j_e1_jp_p93&ch=reg
Laccase is reversibly inhibited by peroxide, as observed when using ABTS as an electron mediator and even when directly contacting the enzyme at a modified carbon electrode. See the publication provided by Imad :-) you could also compare your manganese peroxidase activity to that of commercial catalase. Ross.
Update: I checked the MnP activity with another protocol. This time i monitored the Mn3+ production by measuring UV absorbance at 310 nm. This one worked, although the reaction happens very fast (10-30 seconds). But the trend of results make sense.
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