Date of publication: 2017-07-08 20:44
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For example, the pepsinogen secreted by the stomach becomes active under an acidic pH, turning into the enzyme pepsin. Other well-known zymogens are trypsinogen and chymotrypsinogen, enzymes that are secreted by the exocrine pancreas and which become trypsin and chymotrypsin respectively.
Initially the substrate does not fit perfectly into the active site of the enzyme. When the substrate binds to the active site, this changes the shape of the active site and only then does it perfectly fit the substrate. As the substrate binds it changes the shape of the active site and this weakens the bonds in the substrate and therefore reduces the activation energy. This model is a more precise version of the lock and key one. The reason for this is that it explains why some enzymes can bind to many different substrates. If the shape of the active site changes when a substrate binds, this allows many different but similar substrates to bind to the one enzyme.
575 - Biotic and Abiotic Factors
576 - Homeostatic Evolution
577 - Homeostatic Disruptions
578 - Plant & Animal Defenses
579 - Development: Timing & Coordination
575 - Mechanisms of Timing & Control
576 - Behavior & Natural Selection
According to the lock and key, enzyme functionality depends entirely on the integrity of the activation center, a molecular region with specific spatial characteristics. After denaturation, the spatial conformation of the protein is modified, the activation center is destroyed and the enzyme loses its catalytic activity.
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