Friday, February 27, 2009
Proteolytic degradation can be a major problem in protein purification, leading to low yield and poor product purity. Proteases begin to attack as soon as the cells are lysed, and can continue through nearly the entire protocol. Proteases are a problem in any expression system - tissue culture, plant cells, bacteria, or yeast. Serine proteases, the most common class of proteases, include chymotrypsin, plasmin, thrombin, kalligrein, proteinase K, and trypsin. Other common types of proteases are aminopeptidases, cysteine proteases, aspartic acid proteases, and metalloproteases. With such diversity of proteolytic activity, it's usually a good idea to use a broad-spectrum protease inhibitor cocktail that will cover everything that might be in your sample. Many are available in convenient 100x or 500x concentrate solutions. Occasionally, your target protein will be sensitive to one or more proteases, in which case care should be taken in choosing protease inhibitors that don't interfere with the enzymatic activity of the target. Check out the products on this page to find the right protease inhibitor for your application.