Chapter 13: Enzyme Enzyme: Biological catalyst (normally a protein) that functions to speed up the rate of a biological reaction, but is not altered or consumed by the rxn. Have high catalytic power-catalyze fast Very specific-catalyze a single rxn Require activation energy Speed up rxn by lowering amt of activation required to start rxn. Bring rxn to equilibrium rather than completion Often have co-factors- non-protein components important in catalysis o Organic (CoA, NAD, NADP, Prosthetic Groups[ Heme, Biotin]) o Inorganic (Zn**, Mg**) Models for Enzyme Action: 1. Lock & Key: enzyme active site perfectly matches the shape of the substrate, only allows 1 substrate to bind to the active site and be converted to product 2. Induced Fit: Substrates fit into active site, both enzyme and substrate change shape. Enzymes are not as rigid as one thought, more flexible and dynamic, has been confirmed by X-ray crystallography Types of Kinetic Energy: 1. vibrational 2. rotational 3. translational Substrates (S): the substances upon which an enzyme acts (reactants) Products: the substances produced by chemical modification of substrates Active Site: the specific region on/in an enzyme where substrates bind and where the catalytic rxn occurs. Transition State: the unstable (most energized) intermediate formed in an enzymatic rxn that has properties of both the substrate and the product. -stabilized by enzyme Activation Energy: the threshold energy required to produce a chemical rxn. Free Energy: difference in energy b/t products and reactants. Six Classes of Enzymes: 1. Oxidoreductases: catalyze oxidation-reduction rxns; add/remove electrons/protons from its substrate. o Includes dehydogenases, oxidases, reductases, peroxidases. 2. 3. 4. 5. 6. o Asians have worse hangovers b/c have more active form of Alcohol dehydrogenase. o Acetaldehyde is toxic, dehydrogenase produces acetyl-CoA Transferases: transfer a functional group from one molecule to another o Includes: amino, phosphoryl, methyl, acyl o ex: hexokinase Hydrolases: cleave bonds by adding a water molecule o Includes: esterases, phosphatases, peptidases, lipases, glycosidases) o ex: Phospholipase A2. Lyases: remove functional groups via non-hydrolytic rxns. Often result in double bond, o Includes: decarboxylases, deanimases, dehyrateses o Ex: phenylalanine Ammonia Lyase Isomerases: catalyze rearrangements of functional groups within a molecule o Mustases: transfer functional groups from one position to another o Epimerases: invert functional groups about asymmetric carbons. o Ex: Triose Phosphate Isomerase Ligases: use the energy from ATP hydrolysis to form bonds b/t two substrate molecules o Form C-C, C-S, C-O & PO32- ester bonds o Ex: Acetyl-CoA Carboxylase Enzyme Commission Nomenclature (EC Numbers): Every enzyme has a unique # series that precisely describes its chemical rxn. EC 1: oxidoreductases EC 2: transferases EC 3: hydrolases EC 4: lyases EC 5: isomerases EC 6: ligases