Published: 24.09.2018 20:59

Describe the structure of an enzyme active site

«Describe the structure of an enzyme active site» in pictures.

Proteins as enzymes

Nature of Active Site and Substrate Interaction:

Enzymes have varying degrees of specificity. Some enzymes have absolute specificity for one substrate and no others, while other enzymes react with substrates with similar functional groups, side chains, or positions on a chain. The least specific enzymes catalyze a reaction at a particular chemical bond regardless of other structural features.

Enzyme structure and function - Wikiversity

The enzyme’s active site binds to the substrate. Since enzymes are proteins, this site is composed of a unique combination of amino acid residues (side chains or R groups). Each amino acid residue can be large or small weakly acidic or basic hydrophilic or hydrophobic and positively-charged, negatively-charged, or neutral. The positions, sequences, structures, and properties of these residues create a very specific chemical environment within the active site. A specific chemical substrate matches this site like a jigsaw puzzle piece and makes the enzyme specific to its substrate.

Chemistry for Biologists: Enzymes

The graph shows the typical change in an enzyme's activity with increasing temperature. The enzyme activity gradually increases with temperature until around 87ºC, or body temperature. Then, as the temperature continues to rise, the rate of reaction falls rapidly, as heat energy denatures the enzyme.

Enzyme inhibitors are molecules or compounds that bind to enzymes and result in a decrease in their activity. An inhibitor can bind to an enzyme and stop a substrate from entering the enzyme's active site and/or prevent the enzyme from catalyzing a chemical reaction. There are two categories of inhibitors.

Much experimental work is devoted to gaining an understanding of the nature of the active site in an enzyme. Since enzymes are proteins, the nature of amino acid side chains in the vicinity of the active site is important. The specific amino acid side chains have been determined for many enzymes. The active site for carboxypeptidase A will be used to illustrate the principles involved as shown in the graphic on the left.

Many enzymes only work if bound to non-protein helper molecules called cofactors and coenzymes. Binding to these molecules promotes optimal conformation and function for their respective enzymes. These molecules bind temporarily through ionic or hydrogen bonds or permanently through stronger covalent bonds.

Enzymes are responsible for many of the chemical processes that take place in animals, plants and microbes. They play a critical role in all life on Earth. Because every enzyme has a specific role and function, a change in its tertiary structure would cause the enzyme to be impaired in its function.

Cellular needs and conditions vary from cell to cell and change within individual cells over time. For example, a stomach cell requires a different amount of energy than a skin cell, fat storage cell, blood cell, or nerve cell. The same stomach cell may also need more energy immediately after a meal and less energy between meals.

Enzymes catalyze chemical reactions by lowering activation energy barriers and converting substrate molecules to products.

Many things can effect the tertiary structure of enzymes, which includes the active site, including heat (for example, boiling), freezing, and pH change.