Multiple effects of sodium dodecyl sulfate on chromogenic catalysis of tetramethylbenzidine with horseradish peroxidase

In this work, the chromogenic catalysis of 3,3’,5,5’-tetramethylbenzidine (TMB) with horseradish peroxidase (HRP) in presence of hydrogen peroxide (H2O2), the most widely used chromogenic reaction in enzyme linked immunosorbent assay (ELISA) was deeply studied in the medium containing sodium dodecyl sulfate (SDS). The effects of SDS on the catalytic efficiency and the kinetic behaviors of chromogenic catalysis of HRP–H2O2–TMB were systematically investigated. It was found that the catalysis of HRP–H2O2–TMB follows a ping-pong kinetic mechanism in SDS solutions based on the theoretical model of double substrates enzymatic kinetics. Particularly, multiple significant effects of SDS in different reaction stages have been summarized as follows: the solubilizer of TMB at the early stage of reaction, the promoter of electron transfer at the happening stage of reaction, the stabilizer of blue chromogens at the end of the reaction as well as the binder of HRP during the course of reaction. The results have shown that the first three effects of SDS prevail when SDS concentration is less than 2.5 mM and leading to the catalytic efficiency increase significantly with SDS concentration. However, once SDS concentration is over 2.5 mM, the bonding of SDS on HRP by the strong electrostatic and hydrophobic interaction render SDS act as inhibitors for HRP. The present work may provide feasible means for purposive tailor the chromogenic catalysis of TMB with HRP and improve its chromogenic performance in biochemical detection.