TEV protease is a highly specific cysteine protease with the highest catalytic efficiency. Its identification sequence is ENLYFQ ' position can also be G, A, M, C, or H(1). TEV proteases are typically used to remove affinity purification tags from fusion proteins, such as Glutathione S-transferase (GST), His or other tags for removing fusion proteins. TEV proteases have His tags, which can be easily removed from reactions using nickel affinity resins, so they are suitable for digestion reactions of fusion proteins with His tags, while recombinant proteins with His tags that are not fully digested, excised His tags, and TEV Protease (His-tag) can be removed by means of nickel column binding, resulting in a flow-through solution ( Flow-through) with the desired target protein. During practical operation, in order to preserve the structure and biological activity of the protein of interest as much as possible, it is recommended to cut overnight with TEV Protease enzyme at 4 -9.0, and when the pH is less than or equal to 5, it reduces or even loses enzyme activity.