PROTEASES (or peptidases): hydrolytic enzymes involved in protein digestion. With their action, proteases are able to break the peptide bonds that bind the various amino acids and from which repeated protein molecules originate.
| endopeptidases | exopeptidase |
| They split the peptide bonds within the protein molecule, giving rise to peptides of various lengths. | Hydrolyze peptide bonds located at the ends of the amino acid chain. |
ORIGIN | |
| Gastric and pancreatic | Pancreatic and intestinal |
- Pepsin: produced by the peptic cells of the stomach in an inactive form (pepsinogen). Activated by hydrochloric acid. It mainly intervenes on peptide bonds that bind aromatic amino acids (such as tyrosine, tryptophan and phenylalanine). - Trypsin: produced by the exocrine pancreas in inactive form (trypsinogen). Activated by duodenal enteropeptidase. It mainly intervenes on peptide bonds that engage basic amino acids (such as arginine and lysine) - Chimotripsin: produced by the exocrine pancreas in inactive form (chymotrypsinogen). Activated by trypsin. It mainly intervenes on peptide bonds that bind aromatic amino acids (such as tyrosine, tryptophan and phenylalanine). - Elastase: produced by the exocrine pancreas in an inactive form (pre-pro-elastase). Activated by trypsin. Unique enzyme capable of attacking elastin and as such very important for the digestion of meat foods. | - Carboxypeptidase: produced and secreted by the exocrine pancreas partly in active form and partly in inactive form. They intervene on the peptide bonds placed at the carboxyl end of the amino acid chain. - Aminopeptidases: produced and secreted by the duodenal mucosa. They intervene on the peptide bonds placed at the carboxyl end of the amino acid chain. - Dipeptidase: secreted by the enterocytes of the small intestine, hydrolyze the peptide bond which holds together single amino acid pairs |
Proteases used for the digestion of food-borne proteins represent only a small part of the large family to which they belong. If we think that enzymes, like many hormones, are protein molecules, we realize how important the role played by proteases is. What better way to regulate the activity of these molecules than to degrade them if necessary with specific proteases? Here then is that the cells of the immune system contain proteases to digest the cell membrane of foreign microorganisms, which in turn (we are talking about bacteria) have on the one hand the ability to secrete proteolytic enzymes to invade the cell and on the other hand to release protein toxins (exotoxins) from which we must defend ourselves. Some plasma proteases, such as antithrombin III and plasmin, play an important role in coagulation, preventing excessive activation of this mechanism, which is instead enhanced by thrombin (also belonging to the large protease family).
The modulating action of the proteases is therefore fundamental in the regulation of the various bodily functions; if, from protein synthesis, abnormal proteins originate, for example, it is very important that they are degraded as soon as possible. Similarly, in wound healing the scar tissue cannot grow indefinitely, but must be limited by specific proteases. Furthermore, if we consider that proteases degrade and destroy protein molecules, we must expect that factors, including other proteases, can regulate their function and thus prevent the exalted proteolytic phenomena from causing damage to the body's tissues .
Proteolytic phenomena affecting muscle fibers are activated by fasting and prolonged physical exercise in order to produce energy and glucose from some glucogenic amino acids.
Plant proteases are also synthesized by plants in order to defend themselves against pathogens, degrade peptides and modify the structure and function of other proteins. The pineapple stalk (bromelain), papaya (papain) and sprouted seeds (barley malt) are particularly rich. The ingestion of these foods or their extracts helps to regulate the digestive function, helping the action of endogenous proteases released into the digestive tract.
