Enzyme Structure and Function
- Enzyme function is intricately tied to the structure of the active site, enzyme-substrate specificity, and how environmental factors affect the enzyme.
- Their unique three-dimensional structure of enzymes allows them to interact with specific molecules, called substrates, at a region known as the active site.
The Active Site: A Precision-Engineered Region
Definition
Active site
The active site is a small region on an enzyme where the substrate binds. It is formed by a specific sequence of amino acids within the enzyme's overall three-dimensional structure.
Its structure is highly specific, determined by the enzyme’s amino acid sequence and three-dimensional folding.
Key Features of the Active Site
- Shape Complementarity: The active site’s shape matches the substrate, allowing them to fit together.
- Chemical Compatibility: The active site contains amino acids with specific chemical properties (e.g., charge, hydrophobicity) that interact with the substrate.
- Only a few amino acids in the active site are directly involved in catalysis.
- These amino acids are often brought together by the enzyme’s folding, even if they are far apart in the linear sequence.
Enzyme-Substrate Specificity: The Lock-and-Key and Induced-Fit Models
- Enzymes are highly specific, meaning they catalyse only one reaction or a group of closely related reactions.
- This specificity arises from the precise interactions between the enzyme and its substrate.
- This specificity ensures that the enzyme catalyzes only the desired reaction and does not interact with other molecules that do not fit properly into the active site.
The enzyme amylase is specific to the substrate starch, and it catalyzes the hydrolysis of starch into simpler sugars.
