Proteases (also termed proteinase or peptidase) catalyze the hydrolysis of peptide bonds. They are key enzymes in the regulation of cellular processes and are abundant in all cells and tissues. Upon cell lysis proteases are released into the lysate. Some of the proteases pose a significant impediment to the analysis of biochemical processes. They can generate erroneous results concerning the activity, structure, or location of proteins. Within only a few minutes protease activity can destroy the preparations that took several days of work. Protease inhibitors are employed in order to prevent involuntary protein degradation. They may be synthesized in the laboratory or purified from natural sources. ; they are available as individual substances as well as protease inhibitor cocktails.
As proteases evolved, specific natural inhibitors co-evolved, targeting the active center of the enzymes. Protease inhibitors are common in nature, where they have protective and regulatory functions. For instance, about 20 of the nearly 200 proteins of blood serum are protease inhibitors. Various mechanisms are characterized including chemical modification of proteases, competitive binding to the active site or competitive binding to cofactors. Protease inhibitors bind to their target proteins reversibly or irreversibly. Reversibly binding inhibitors may be lost during dialysis or other purification steps. So it is of practical importance to know the mode of action for selecting the appropriate protease inhibitors and preparing solutions and buffers.
Protease inhibitors are supposed to provide specificity so that proteases are blocked but other proteins stay unaffected. Other desired characteristics include solubility and stability. Ideally, the substances are also non-toxic and easy to handle. Scientists at research institutions have relied on the quality of AppliChem’s protease inhibitors for many years. This application note summarizes AppliChem’s protease inhibitors that are available as individual substances to target specific proteases or more convenient, as cocktails specifically designed to inhibit proteases of the most common expression systems.