Structure of enzyme
- 1. Structure of Enzyme Presented by- Bivash Dutta
- 2. CONTENT- Enzyme Structure of enzyme Active site Co-factor Substrate Intracellular enzyme and Extracellular enzyme
- 3. Enzyme Enzymes are biological catalysts that speed up the rate of the biochemical reaction. Most enzymes are three dimensional globular proteins (tertiary and quaternary structure). Some special RNA species also act as enzymes and are called Ribozymes e.g. hammerhead ribozyme.
- 4. Structure of Enzyme Enzyme have either tertiary or quaternary structure. The protein chain folds itself and forms pocket like structure called as active site. The active site of an enzyme is the region that binds substrates, co-factors and prosthetic groups and contains residue that helps to hold the substrate. Active sites generally occupy less than 5% of the total surface area of enzyme. Active site has a specific shape due to tertiary structure of protein. A change in the shape of protein affects the shape of active site and function of the enzyme. Substrate is a substance that is acted upon by enzyme.
- 5. Active Site The region of an enzyme where substrate molecules binds and undergo a chemical reaction. Active site can be further divided into : • Binding site – it choose the substrate and binds it to the active site. • Catalytic site – it perform the catalytic action of an enzyme
- 6. Co-factors A cofactor is a non-protein chemical compound that is required for the protein's biological activity. Many enzymes require cofactors to function properly. Cofactors can be considered "helper molecules" that assist enzymes in their action. An enzyme with its co-factor removed is designated as apoenzyme. The complete complex of a protein with all necessary small organic molecules, metal ions and other components is termed as holoenzyme of holoprotein.
- 7. Substrate The reactant in a biochemical reaction is termed as substrate. Enzymes catalyze chemical reactions involving the substrate(s). In the case of a single substrate, the substrate bonds with the enzyme active site, and an enzyme-substrate complex is formed. The substrate is transformed into one or more products, which are then released from the active site. The active site is then free to accept another substrate molecule.
- 8. Intracellular enzyme and Extracellular enzyme Intracellular enzymes are synthesized and retained in the cell for the use of cell itself. They are found in the cytoplasm, nucleus, mitochondria and chloroplast. Example : Oxidoreductase catalyse biological oxidation. Enzymes involved in reduction in the mitochondria. Extracellular enzymes are synthesized in the cell but secreted from the cell to work externally. Example : Digestive enzyme produced by the pancreas, are not used by the cells in the pancreas but are transported to the duodenum.