Correct option is C
The correct answer is: (3) Superoxide dismutase is an apoplastic enzyme involved in the formation of superoxide.
Explanation:
Superoxide dismutase (SOD) is not involved in the formation of superoxide, but rather in its dismutation (conversion) into hydrogen peroxide. SOD catalyzes the conversion of the superoxide anion (O₂⁻) into hydrogen peroxide (H₂O₂), which is another reactive oxygen species. In this process, SOD protects cells from oxidative damage caused by the accumulation of superoxide radicals. Superoxide itself is generated by NADPH oxidases during the oxidative burst and is subsequently detoxified by enzymes such as SOD.
Information Booster:
NADPH oxidase is a membrane-spanning protein that produces superoxide radicals by transferring electrons from NADPH to oxygen, initiating the oxidative burst.
In Arabidopsis, the production of reactive oxygen species is controlled by the Atrboh gene family, which encodes NADPH oxidases responsible for the generation of superoxide radicals during stress responses.
Superoxide dismutase (SOD) does not produce superoxide but converts superoxide to hydrogen peroxide, an important step in protecting cells from oxidative stress.
The apoplastic location of SOD helps detoxify superoxide in the intercellular space, not contribute to its formation.
Additional Knowledge:
FAD (option 4) plays a role in NADPH oxidase activity and is involved in electron transfer during the formation of superoxide, but superoxide dismutase is not responsible for its formation.
NADPH oxidase (option 1) is correctly described as a plasma membrane-spanning protein responsible for the generation of superoxide during the oxidative burst.
Respiratory burst oxidase homolog (Atrboh) (option 2) are the Arabidopsis genes that encode the NADPH oxidases, which are crucial for reactive oxygen species production during defense responses.
