Glutathione is maintained in reduced state by the help of ?
**Core Concept**
Glutathione is a tripeptide antioxidant that plays a crucial role in maintaining cellular redox balance. Its reduced state (GSH) is essential for scavenging reactive oxygen species (ROS) and protecting cells from oxidative stress. The enzyme responsible for maintaining glutathione in its reduced state is a key component of cellular antioxidant defense.
**Why the Correct Answer is Right**
Glutathione is maintained in its reduced state by the enzyme glutathione reductase. This enzyme catalyzes the reduction of oxidized glutathione (GSSG) to its reduced form (GSH) using NADPH as a cofactor. The reaction is as follows: GSSG + NADPH + H+ → 2GSH + NADP+. Glutathione reductase is a flavoprotein that contains FAD as a prosthetic group, which is essential for its catalytic activity. The enzyme is found in the cytosol of cells and plays a critical role in maintaining the balance between reduced and oxidized glutathione.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because glutathione peroxidase, while involved in the detoxification of hydrogen peroxide and other ROS, does not maintain glutathione in its reduced state.
**Option B:** This option is incorrect because glutathione S-transferase is an enzyme involved in the conjugation of glutathione with electrophilic compounds, but it does not reduce oxidized glutathione.
**Option C:** This option is incorrect because NADPH oxidase is an enzyme that generates superoxide anion by transferring electrons from NADPH to oxygen, which would actually contribute to oxidative stress rather than maintaining glutathione in its reduced state.
**Clinical Pearl / High-Yield Fact**
Glutathione reductase is inhibited by certain drugs, such as metronidazole and nitrofurantoin, which can lead to increased levels of oxidized glutathione and decreased antioxidant capacity in cells.
**Correct Answer: C. NADPH**