H2O2
Summary
Hydrogen peroxide (H2O2) is a reactive oxygen species and byproduct of cellular metabolism. It is produced by NADPH oxidase in phagocytes and other enzymes; catalase and glutathione peroxidase enzymatically break it down to prevent oxidative damage.
Detail
H2O2 is an important signaling molecule and oxidative stress mediator. In phagocytes (neutrophils, macrophages), NADPH oxidase generates H2O2 as part of the respiratory burst during bacterial killing. Excess H2O2 can damage cellular components, so it is rapidly neutralized by catalase (present in peroxisomes and RBCs) and glutathione peroxidase (present throughout cells). In chronic granulomatous disease, NADPH oxidase is defective, leading to inability to produce H2O2 and recurrent infections with catalase-positive organisms. H2O2 is also used therapeutically (wound cleaning, antiseptic) and in peroxide oxidase assays for laboratory testing. Understanding H2O2 metabolism is essential for board exams when discussing oxidative stress, phagocyte function, and genetic immunodeficiencies.
Sources
- First Aid for USMLE Step 1
- Lehninger Biochemistry
- Robbins Pathology
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