A New Fluorescent Method for Measuring Peroxiredoxin Enzyme Activity Using Monobromobimane

A novel fluorometric method is presented for accurately quantifying peroxiredoxin (Prx) enzyme activity in vitro. The rate-limiting step in the Prx-catalyzed reaction is the dissociation of peroxide. To avoid interference from catalase, we developed an assay using tert-butyl hydroperoxide (t-BOOH) as a substrate for specific Prx activity measurement. The assay involves incubating the enzyme substrates 1,4-dithio-DL-threitol (DTT) and t-BOOH in a suitable buffer at 37 °C for 10 min in a known volume of Prx enzyme. Following incubation, the reagent monobromobimane (mBB) is added to terminate the enzymatic reaction and produce a fluorescent product. Prx activity is subsequently determined by measuring thiol fluorescence, with reaction conditions optimized using a Bland-Altman plot. The efficacy of this novel protocol was rigorously validated by comparing Prx activity measurements from paired samples with those generated by a reference assay. A correlation coefficient of 0.995 was observed between the two methods, demonstrating superior precision and reliability compared to existing methods. The mBB-Prx protocol offers a significant safety advantage by using t-BOOH as a substrate for Prx activity measurement. As catalase does not catalyze t-BOOH dissociation, including sodium azide is unnecessary. Moreover, the method obviates the need for concentrated acids to terminate the Prx enzymatic reaction, as the mBB reagent efficiently inhibits Prx activity. This streamlined approach simplifies the assay and significantly improves its safety and usability, providing users with a reliable and convenient tool. The convenience of this method allows users to focus on their research without worrying about safety or complex procedures.