ALDH3A1 comprises approximately 10-40% of the water-soluble protein in the mammalian cornea.[20][21] Direct exposure to UVR and molecular oxygen, make the cornea susceptible to ROS and 4HNE. Studies in which rabbits were transfected with genes that allow them to overexpress human ALDH3A1 in their corneal stromal fibroblasts document ALDH3A1's most critical function is to protect the cornea from oxidative stresses. In the cornea ALDH3A1: (1) prevents the formation of 4-HNE protein adducts that would impeded proteins’ function; (2) is more effective at metabolizing 4-HNE than other comparable agents such as glutathione (GSH); (3) protects the corneal cells from 4-HNE induced apoptosis; (4) reduces consumption of GSH by relieving 4HNE GSH adducts; (5) and relieves 4-HNE’s inhibition of the 20S protease activity.[22]