Peroxidase-like catalytic substrates (POD substrates)

Peroxidase-like catalytic substrates are a diverse group of chemical compounds that serve as electron donors in reactions mediated by peroxidase enzymes or peroxidase-mimicking nanomaterials, known as nanozymes. These substrates, such as 3,3',5,5'-tetramethylbenzidine (TMB), 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and o-phenylenediamine (OPD), are fundamental to diagnostic biotechnology, where they are used in ELISA and immunohistochemistry to produce colorimetric or fluorescent signals for the detection of specific biomarkers. In therapeutic contexts, the term can also refer to endogenous molecules like hydrogen peroxide (H2O2), which are converted by peroxidase-like catalysts into cytotoxic reactive oxygen species (ROS) to target and destroy cancer cells or pathogens. While these substrates are essential for the operation of diagnostic and catalytic therapeutic systems, they are not biological targets in the traditional sense; rather, the enzymes or nanozymes that act upon them are the primary focus of therapeutic development. Their utility lies in their predictable redox behavior and their ability to generate measurable signals or localized oxidative stress.

Other names

Chromogenic peroxidase substratesFluorogenic peroxidase substratesPeroxidase-mimetic substratesRedox-active substratesNanozyme substrates

These substrates act as electron donors in reactions catalyzed by peroxidase enzymes or peroxidase-mimicking nanozymes. In the presence of hydrogen peroxide, the substrate is oxidized to form a detectable colored, fluorescent, or chemiluminescent product, or highly reactive radicals that can induce localized oxidative stress and cell death.