Which compound serves as substrate for HRP in immunohistochemical assays?

Which compound serves as substrate for HRP in immunohistochemical assays?

• A. Naphthol-AS-phosphate
• B. Hydrogen peroxide
• C. 3,3'-diaminobenzidine
• D. Tetramethylbenzidine

Answer: (B)

Hydrogen peroxide is what HRP uses to drive the color-producing reaction. In immunohistochemistry, HRP catalyzes the oxidation of a chromogenic substrate (for example, DAB or TMB), but this oxidation requires hydrogen peroxide as the oxidizing agent. Without hydrogen peroxide, the enzyme cannot transfer oxygen to the chromogen, and no color develops. The other options either refer to substrates used with different enzymes (such as alkaline phosphatase) or are the chromogenic substrates that are oxidized by HRP, not the actual oxidant the enzyme relies on.

Hydrogen peroxide is what HRP uses to drive the color-producing reaction. In immunohistochemistry, HRP catalyzes the oxidation of a chromogenic substrate (for example, DAB or TMB), but this oxidation requires hydrogen peroxide as the oxidizing agent. Without hydrogen peroxide, the enzyme cannot transfer oxygen to the chromogen, and no color develops. The other options either refer to substrates used with different enzymes (such as alkaline phosphatase) or are the chromogenic substrates that are oxidized by HRP, not the actual oxidant the enzyme relies on.