GSTO1, also known as p28 or GSTTLp28, is a protein that localizes to the cytoplasm and contains both an N-terminal and a C-terminal GST domain. In mouse, the encoded protein acts as a small stress response protein, likely involved in cellular redox homeostasis. This protein has dehydroascorbate reductase activity and may function in the glutathione-ascorbate cycle as part of antioxidant metabolism.