enzymes

• Allosteric regulation is a type of enzyme regulation where a molecule binds to a site on the enzyme that is distinct from the active site, causing a change in the enzyme's activity.
• Enzymes are all proteins with high molecular weight, acting as catalysts, being active outside the cell, water soluble, amphoteric molecules, and have specificity.
• In order to effectively initiate a reaction, collisions must be sufficiently energetic to break chemical bonds, this energy is known as the activation energy.
• As the temperature rises, molecules move faster and collide more vigorously, greatly increasing the likelihood of bond breakage upon collision.
• The Fischer “lock - and - key” hypothesis, proposed by Fischer in 1890, states that structures do not change their shape during the binding process.
• The Koshland “induced - fit” hypothesis, proposed by Koshland in 1958, suggests that X-ray diffraction analysis and NMR data have revealed differences in structure between free and substrate-bound enzymes, leading to a conformational change and a mechanism that could help to achieve high degree of specificity.
• Factors affecting enzyme activity include temperature, which can increase with a rise in temperature, bringing molecules closer for reaction, with most enzymes having an optimal temperature of 37 o C.
• Cold water fish dies at 30 o C, thermophylic enzymes may have activity at 100 o C.
• Most enzymes denature at 70 o C.
• Extreme pH causes denaturation.
• Enzymes make and break intra and intermolecular bonds, causing the active site to be distorted.
• Enzyme inhibitors can be irreversible or reversible, with irreversible inhibitors combining with the functional groups of the amino acids in the active site, and reversible inhibitors can be washed out of the solution of enzyme by dialysis.
• Enzyme inhibitors can be competitive or non-competitive, with competitive inhibitors competing with the substrate molecules for the active site, and non-competitive inhibitors not being influenced by the concentration of the substrate, but inhibiting by binding irreversibly to the enzyme but not at the active site.
• Examples of enzyme inhibitors include nerve gases and pesticides, containing organophosphorus, which combine with serine residues in the enzyme acetylcholine esterase, and cyanide, which combines with the Iron in the enzymes cytochrome oxidase.
• Enzyme regulation can be achieved by using enzyme inhibitors, such as irreversible inhibitors which combine with the functional groups of the amino acids in the active site, and reversible inhibitors which can be washed out of the solution of enzyme by dialysis.
• Enzyme regulation can also be achieved by using enzyme inhibitors that are competitive or non-competitive, with competitive inhibitors competing with the substrate molecules for the active site, and non-competitive inhibitors not being influenced by the concentration of the substrate, but inhibiting by binding irreversibly to the enzyme but not at the active site.
• Enzyme regulation can be achieved by using enzyme inhibitors that are irreversible or reversible, with irreversible inhibitors combining with the functional groups of the amino acids in the active site, and reversible inhibitors can be washed out of the solution of enzyme by dialysis.
• Once the product has been released from the enzyme, the enzyme can be used again to catalyze another reaction with another molecule of substrate.
• The enzyme catalyzes the reaction by lowering the activation energy required for the reaction to occur, allowing it to proceed more quickly at physiological temperatures.
• Transferases catalyze the transfer of functional groups between molecules.
• Oxidoreductases catalyze oxidation-reduction reactions.
• Enzymes are classified into six main groups based on their function: oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases.
• Enzyme-substrate complex is formed when the substrate binds to an active site on the enzyme.
• Uncompetitive inhibitors bind only when the substrate is present, forming an ESI complex with the substrate and inhibitor bound together.
• Non-competitive inhibition is a type of enzyme regulation where a molecule binds to a site on the enzyme that is distinct from the active site, causing a change in the enzyme's shape and reducing its activity.
• Enzymes can be inhibited by competitive or non-competitive mechanisms.
• Non-competitive inhibition involves the binding of an inhibitor at a different site than the active site, leading to a conformational change in the enzyme that reduces its catalytic efficiency.
• Competitive inhibition occurs when an inhibitor competes with the substrate for binding to the active site of the enzyme.
• Substrates must fit perfectly into the active site to form an enzyme-substrate complex.
• Active sites have specific shapes and charge distributions that allow them to interact only with certain types of molecules.
• Catalytic triad consists of three amino acids that work together to facilitate chemical reactions.
• Isomerases catalyze isomerization reactions.
• Lyases catalyze addition/elimination reactions without water involvement.
• Hydrolases catalyze hydrolysis reactions.
• Competitive inhibition occurs when an inhibitor competes with the substrate for binding to the active site, resulting in reduced enzymatic activity.
• Allosteric inhibition involves the binding of an allosteric inhibitor to a regulatory site on the enzyme, which causes a conformational change that decreases the affinity of the active site for the substrate.
• Feedback inhibition is a mechanism used by cells to regulate metabolic pathways by using end products as signals to turn off further production.
• The induced-fit model proposes that enzymes undergo slight changes in conformation upon binding to their substrates.
• The catalytic triad is made up of histidine (His), aspartate/glutamate (Asp/Glu), and serine (Ser).
• The lock-and-key model suggests that enzymes are rigid structures that match exactly with their substrates.