Enzymes PDF

Enzymes **   MLO7.**    Describe the function of enzymes, the mechanism of enzyme catalysis, and inhibition. Enzymes are biological catalysts that will catalyse or speed up chemical reactions Enzymes lower the activation energy of a reaction so that it is easier to overcome Enzymes tend to be gl...

Enzymes **   MLO7.**    Describe the function of enzymes, the mechanism of enzyme catalysis, and inhibition. Enzymes are biological catalysts that will catalyse or speed up chemical reactions Enzymes lower the activation energy of a reaction so that it is easier to overcome Enzymes tend to be globular proteins, are soluble in water and have a highly specific activity that's determined by the structure itself Induced fit model: - Active site is not quite the right shape as the substrate - Once substrate nears enzyme active site, protein changes shape to accommodate substrate - Straining chemical bonds and thus lowering activation energy by stabilising the transition state of the substrate Key factors that affect enzyme function: - Temperature: enzyme may get denatured at extremes - pH: enzyme may get denatured - Inhibition: cofactors and coenzymes The protein component without its cofactor is called an apoenzyme ( cofactors are the nonprotein portion) - Organic cofactors are referred to as coenzymes - Inorganic cofactors include several cations such as Zn2+, Mg2+ etc. Covalent catalysis: - Temporary covalent bond forms between the enzyme and substrate, forming an acyl-enzyme intermediate as part of the catalytic process A white background with blue text Description automatically generated Oxidoreductases: - An enzyme that catalyses the transfer of electrons from one molecule to another (catalyse redox reactions) - Eg. Dehydrogenases, oxidases, reductases, oxygenases Transferases: - An enzyme that catalyses transfer of a specific functional group from one molecule to another - Eg. Kinases, phosphorylases, aminotransferases Hydrolases: - An enzyme that catalyses the hydrolysis of a chemical bond in biomolecules, utilising water as a hydroxyl group donor during substrate breakdown - Eg. Peptidases, glycosylases, lipases, nucleosidases, nucleases, phosphatases Lyases: - An enzyme that catalyses cleavage through means other than hydrolysis or oxidation, often forming a new double bond, adding a group to the double bond, or forming a new ring structure - Eg. Decarboxylases, aldolases, synthases Isomerases: - An enzyme that converts one molecule from one isomer to another - Facilitates intramolecular rearrangements - Eg. Mutases, epimerases, racemases Ligases: - An enzyme that uses ATP to form bonds, joining two large molecules by forming a new chemical bond - Eg. Carboxylases, synthetases Translocases: - An enzyme that assists in moving another molecule across a membrane, such as a cell membrane or the membrane of a membrane bound organelle - Typically using ATP of proton motor force Chymotrypsin: - Catalyses the hydrolysis of proteins (peptide bonds) - Chymotrypsin is a serine protease - On the active site, there is an oxyanion hole; a pocket that stabilises a transition state negative charge - Catalytic triad results in delocalised area of negative charge - Negative charge on O-atom Enzyme kinetics: - V~max~: the reaction rate at the point where the enzyme is saturated with substrate - K~m~: the substrate concentration required for half maximal enzyme activity. It reveals the affinity of the enzyme to the substrate and reveals how easily an enzyme can be saturated by the substrate Enzyme inhibition: the reduction or cessation of enzyme activity caused by the presence of an inhibitor - Competitive inhibition - Non-competitive inhibition - Uncompetitive inhibition: inhibitor binds only to e/s complex preventing reaction from proceeding, decreasing both V~max~ and K~m~ - Mixed inhibition: inhibitor binds to allosteric site, changing enzyme activity - Irreversible inhibition: inhibitors form a covalent bond with enzyme, permanently inactivating it, V~max~ is decreased Moodle recap quiz Q: Enzymes have a 3-D shape due to which type of protein structure? A: Tertiary structure Q: Which bonds can be found in the structure of enzymes?\ A: Hydrogen, disulphide, peptide, ionic Q: Which factors affect the rate of enzyme activity?\ A: pH, substrate concentration, temperature, enzyme concentration