– ERO1-Like Protein α (ERO1L) is an enzyme that belongs to the EROs family. ERO1L is expressed at high level in esophagus and upper digestive tract. ERO1L is an essential oxidoreductase that oxidizes proteins in the endoplasmic reticulum to produce disulfide bonds. ERO1L acts by oxidizing directly P4HB/PDI isomerase through a direct disulfide exchange. It associates with ERP44, demonstrating that it does not oxidize all PDI related proteins and can discriminate between PDI and related proteins. Its reoxidation probably involves electron transfer to molecular oxygen via FAD. ERO1L may be responsible for a significant proportion of reactive oxygen species (ROS) in the cell. ERO1L responses to temperature stimulus, protein thiol-disulfide exchange, protein folding with or without chaperone cofactor and transport.