Enzymes

• enzymes are biological catalysts that either

  1. string together nucleotides and amino acids to make DNA and proteins
  2. break down sugar & fat into energy and toxins in the liver
• enzymes increase reaction rate by lowering the activation energy and remain unchanged during the reaction
• nearly all enzymes are globular proteins and therefore have tertiary structure
• Active site is a region within an enzyme that fits the shape of the reacting molecule, known as the substrate; contains amino acid R groups that bind the substrate.
• substrates must fit perfectly into an active site to form ES complex
• Lock and key model of enzyme action states that the substrate will only form product if they fit the active site.
• Enzyme specificity is the ability of an enzyme to only act on one substrate or class.
• The lock and key model explains the loss of activity when enzymes denature.
• Induced fit hypothesis states that the enzyme slightly changes shape (conformation) to fit the substrate.
• Enzyme names usually end in -ase.
• Oxidoreductases catalyze redox reactions, with oxidases causing oxidation and dehydrogenases causing dehydration.
• Transferases transfer functional groups between two compounds.
• Hydrolases catalyze hydrolysis reactions that split compounds into two products.
• Lyases add or remove without hydrolysis.
• Ligases join two substrates using ATP energy.
• Isomerases catalyze rearrangement (isomerization) of atoms within a substrate.
• Enzymes reach maximum activity when the substrate concentration eventually reaches the saturation point.
• Enzyme concentration affects the amount of substrate bound to the enzyme.
• Enzymes are most active at the optimum pH.
• The body's pH is 7.4.
• Extreme levels of pH can lead to denaturation, disrupting the tertiary structure of enzymes.
• Increasing the temperature increases the number of collisions, resulting in higher catalytic activity.
• Enzymes have their highest catalytic activity at the optimum temperature, usually around 30°C.
• High temperatures can lead to denaturation, disrupting the tertiary structure of enzymes.
• factors affecting enzymes are substrate & enzyme concentration, temperature, and pH
• enzyme regulation can occur through allosteric enzymes, feedback control, and covalent modifications
• Allosteric enzymes bind with a regulator molecule at the allosteric site, which is different from the active site.
• Allosteric enzymes change shape in response to positive and negative regulators.
• Positive regulators cause allosteric enzymes to change shape, allowing binding, and increase the reaction rate.
• Negative regulators cause allosteric enzymes to change shape, preventing binding, and decrease the reaction rate.
• Feedback control is a specific type of allosteric enzymatic activity regulation that depends on the product amount.
• High end product level causes allosteric enzymes to become negative regulators.
• Low end product level causes allosteric enzymes to become positive regulators.
• Zymogens, also known as Pro-Enzymes, are produced in their inactive form and are activated when needed.
• Zymogens become active by removal of specific parts by proteolytic cleavage.
• Zymogens include digestive enzymes, protein hormones (insulin), and blood clotting enzymes.
• Phosphorylation is a type of covalent modification through which an enzyme is deactivated or activated.
• An inactive enzyme undergoes covalent modification.
• Phosphorylation is activated by the addition of a phosphate group.
• Phosphorylation is deactivated by the removal of a phosphate group.