Chymotrypsin Protein Hydrolysis

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Chymotrypsin Protein Hydrolysis Although an enzyme called pepsin begins to digest protein molecules while they are in our stomach, most of the digestion of protein takes place after the food leaves the stomach and moves into the small intestines. Here enzymes like trypsin, chymotrypsin, elastase, carboxypeptidase, and aminopeptidase convert protein molecules into amino acids, dipeptides, and tripeptides. The dipeptides and tripeptides are converted to amino acids by other enzymes. Once the amino acids are free, they can move into the blood stream and circulate throughout our body. In all forms of digestion (whether of proteins, carbohydrates, or fats), larger molecules are broken down into smaller molecules by a reaction with water in which a water molecule is split in two, with each part joining a different product molecule. This type of reaction is called hydrolysis. Remember that proteins are long chains of amino acids linked together by amide functional groups called peptide bonds. When protein molecules are digested, a series of hydrolysis reactions convert them into separate amino acids. RCONR2 + H2O RCO2H + HNR2 In the laboratory, the reaction above is very slow unless a strong acid catalyst is added to mixture, yet in the small intestines, where the conditions are essentially neutral rather than acidic, most of the hydrolysis of proteins takes place rather quickly. The reason, as we have seen, is the presence of enzymes. To get a general idea of how enzymes do their work, lets look at a proposed mechanism for the hydrolysis of peptide bonds in protein molecules as mediated the enzyme chymotrypsin. For an enzyme-mediated reaction to take place, the reacting molecule or molecules, called substrates, must fit into a specific section of the enzymes structure called the active site. Each active site has (1) a shape that

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