Proteases perform many beneficial functions that are essential to life, but uncontrolled they can be dangerous. Protease inhibitors are used as the major form of control once the protease has been activated. In higher organisms, there is a delicate balance between proteases and their natural inhibitors to help control the activation and catabolism of many intra- and extra-cellular proteins. In mammals, the bloodstream is a major carrier for many glycoproteins that act as protease inhibitors. Protease inhibitors use a reactive site peptide bond to serve as a substrate for various proteases, forming very stable complexes where the inhibitor peptide bond is hydrolysed by the protease extremely slowly, thereby effectively removing the protease from circulation. There are at least eighteen families of protease inhibitors, all of which share a common conformation surrounding the reactive site peptide bond, even though they differ in their global structure. Some members only hydrolyse trypsin, such as chicken ovomucoid, while others hydrolyse both trypsin and chymotrypsin using different inhibitory domains, such as turkey ovomucoid.
Protease inhibitors are ubiquitous in nature. They are widely distributed in plant seeds, particularly in legumes. The presence of these inhibitors in seeds acts as a feeding deterrent, especially in insects where they inhibit midgut proteases. Inhibitors can deter other animals as well; isolated soybean inhibitors have been found to cause enlargement of the pancreas in certain species, such as rat and mouse. Many bacterial species produce protease inhibitors that help them to survive the digestive processes of the gut, such as ecotin in Escherichia coli, which is effective against several different pancreatic proteases because of its flexibility.
Proteases perform many beneficial functions that are essential to life, but uncontrolled they can be dangerous. Protease inhibitors are used as the major form of control once the protease has been activated. In higher organisms, there is a delicate balance between proteases and their natural inhibitors to help control the activation and catabolism of many intra- and extra-cellular proteins. In mammals, the bloodstream is a major carrier for many glycoproteins that act as protease inhibitors. Protease inhibitors use a reactive site peptide bond to serve as a substrate for various proteases, forming very stable complexes where the inhibitor peptide bond is hydrolysed by the protease extremely slowly, thereby effectively removing the protease from circulation. There are at least eighteen families of protease inhibitors, all of which share a common conformation surrounding the reactive site peptide bond, even though they differ in their global structure. Some members only hydrolyse trypsin, such as chicken ovomucoid, while others hydrolyse both trypsin and chymotrypsin using different inhibitory domains, such as turkey ovomucoid. Protease inhibitors are ubiquitous in nature. They are widely distributed in plant seeds, particularly in legumes. The presence of these inhibitors in seeds acts as a feeding deterrent, especially in insects where they inhibit midgut proteases. Inhibitors can deter other animals as well; isolated soybean inhibitors have been found to cause enlargement of the pancreas in certain species, such as rat and mouse. Many bacterial species produce protease inhibitors that help them to survive the digestive processes of the gut, such as ecotin in Escherichia coli, which is effective against several different pancreatic proteases because of its flexibility.
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