What is the role of DTT in cell lysates?

Hello，DTT is a commonly used reduction reagent, it is often used for protein preservation and protein disulfide bond reduction. We know that -SH often acts as the active center of many proteins, -SH is highly reductive, and when it is oxidized, the protein loses its activity. Therefore, when the protein is purified and preserved, a certain amount of DTT is added to the solution to avoid the protein-SH being oxidized and inactivated.