Now let's move on to aspartate proteases, also known as aspertyl proteases. Now the major difference between cysteine proteases and aspirations is the following. In cystine proteases as well as the serum proteases we see that one of the residues inside the active side of the enzyme acts as a nuclear file. But in aspital protease, the residues don't actually act as nuclear files. Instead it's the water that will ultimately act as the nuclear file. Now the similarity between, let's say cysteine protease and aspirin protease is we still have to transform the water into a good nuclear file in the same way that we had to transform the cysteine into a strong nuclear file before the nuclearphilic attack took place.