Nevertheless, there are features that tend to be common in methods for recovery of proteins. After all, proteins are polymers of amino acids with many common features. Certain tissues such as pancreas glands or liver are particularly rich in enzymes. However, some of the enzymes in the mixture when cells are disrupted are proteases. They digest proteins.
Enzymes are proteins, and proteases can digest themselves.
We can take advantage of the change in enzyme activity with pH by changing to a pH where the protease activity is low. The disruption of cells to release enzymes can be carried out at low pH and cold temperatures to minimize losses due to proteolytic activity. Proteins have great specificity that can be used to attach them to other molecules. Attaching an protein to a solid by exploiting this specificity is called affinity chromatography. Sometimes quite pure enzymes can be recovered from a mixture by affinity chromatography, but more often there is a preliminary separation.