Endogenous peroxidase can also be blocked with which of the following reagents?

Endogenous peroxidase can also be blocked with which of the following reagents?

• A. Sodium azide and hydrogen peroxide
• B. Sodium chloride and water
• C. Ethanol and acetone
• D. Detergents

Answer: (A)

Blocking endogenous peroxidase is done to prevent false positive staining in HRP-based detection by inactivating the tissue’s own peroxidase enzymes before applying the antibody. Hydrogen peroxide blocks by oxidizing the heme iron in peroxidases, effectively inactivating the enzyme. Sodium azide provides another way to inhibit peroxidase: it binds to the heme iron and stops the catalytic activity. Using both can offer robust suppression of endogenous activity. The other substances don’t reliably inactivate endogenous peroxidases—salts and water don’t affect the enzyme, simple alcohols can alter tissue antigens, and detergents don’t block the enzyme's activity.

Blocking endogenous peroxidase is done to prevent false positive staining in HRP-based detection by inactivating the tissue’s own peroxidase enzymes before applying the antibody. Hydrogen peroxide blocks by oxidizing the heme iron in peroxidases, effectively inactivating the enzyme. Sodium azide provides another way to inhibit peroxidase: it binds to the heme iron and stops the catalytic activity. Using both can offer robust suppression of endogenous activity. The other substances don’t reliably inactivate endogenous peroxidases—salts and water don’t affect the enzyme, simple alcohols can alter tissue antigens, and detergents don’t block the enzyme's activity.