Few enzymes have one or more sulfhydryl (thiol) groups that are significant to enzymatic activity but that can react upon standing in solution to form inactive disulfide bonds.
Thiol reagents, such as 1,4-dithiothreitol (DTT), are frequently added to the solutions of such proteins to protect them from this reaction as well as to reverse it when it occurs. The reverse reaction works best at slightly alkaline pH. Illustrate the product formed when DTT reacts with a protein disulfide bond to liberate the free thiol groups.
Explain which of the following occurs in this reaction?
The protein disulfide is oxidized
The protein disulfide is reduced
DTT is reduced
DTT is oxidized