Ascorbate peroxidase

Function

Ascorbate peroxidase (APX) catalyzes the conversion of ascorbate and hydrogen peroxide to dehydroascorbate and water thus detoxifying hydrogen peroxide. APX is involved in the glutathione-ascorbate cycle. APX is accumulated in plants in response to heat and drought stress. APX contains a heme group.

Relevance

APX is part of plants antioxidant defense. APX converts H2O2 to water using ascorbate as an electron donor. APX is used in electron microscopy as a genetic tag which can be stained independently of light activation.

Structural highlights

The heme-containing active site of APX contains a His residue (H163 in soybean) which coordinates with the heme and confers stability to the Fe state in the heme.