Chem331 Lect 18 Kinetics
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4/26/17 Enzyme Nomenclature Provides a Naming Enzymes Systematic Way of Naming Metabolic Reactions •Enzyme commission for each enzyme based on the type of reactions. Kind of like IUPAC Oh •Yeah right - the mother of invention – he/she who To finds/discovers/purifies/clones the enzyme, names if. Have Trivial names rule… Lived First recognition of an enzyme and naming – 1833: alcohol precipitate of malt In extract converted starch into sugar – called diatase (first use of suffix –ase) Lisbon Proteases traditionaly are the only enzymes which don’t end in ‘ase’ and use ‘- in’ Enzyme is coined after the Greek for “in yeast” 1050s started need to use a standardized naming: Otto Hofmann-Ostenhof and Dixon & Webb – common, non-systematic names still rule. Enzyme reaction types: Enzymes are classified into six 2) Transferases catalyze group-transfer reactions major classes based on the reaction they catalyze. (functional groups). Many require the presence of coenzymes. A portion of the substrate molecule usually 1) Oxidoreductases catalyze oxidation-reduction reactions. Most of binds covalently to these enzymes or their coenzymes. these enzymes are known as dehydrogenases, but some are called This group includes the kinases! oxidases, peroxidases, oxygenases or reductases. A- + B -> A + B- A-X + B -> A + B-X A is the reductant (e- donar) and B is the oxidant (e- acceptor) A is the donar and B is the acceptor Donor s often a coenzyme NAD+ (ox) +e- + H+ -> NADH (red) ATP + R-OH -> ADP + R-PO4-2 1 4/26/17 3) Hydrolases catalyze hydrolysis. They are a special 4)Lyases catalyze nonhydrolytic and nonoxidative elimination class of transferases, with water serving as the acceptor reactions, or lysis, of a substrate, generating a double bond. In of the group transferred other words these reactions catalyze group elimination to form double bonds. In the reverse direction, lyases catalyze addition of one substrate to a double bond of a second A-B + H O -> A-OH + B-H substrate. 2 A=B + X-Y -> X-A-B-Y A lyase that catalyzes addition reaction in cells is often termed a synthase. ATP -> cAMP + PPi Usually only need one substrate in one direction and two for the reverse! 5) Isomerases catalyze the isomerase reactions. Because these reactions have only one substrate and one product, 6) Ligases catalyze ligation or joining, of two substrates. they are among the simplest enzymatic reactions. These reactions require the input of chemical potential energy of a nucleoside triphosphate such as ATP. i.e. A -> B bond formation coupled to ATP hydrolysis. Ligases are usually referred to as synthetases. Often involved in Names of these enzymes are “substrate isomersase” joining carbon atoms to N, S or O atoms. Ex. - enoyl CoA isomerase or some sort of mutase i.e. phosphoglucomutase Ab + C -> A-C + b A (XTP) + B -> A-B + (XDP + Pi) Sometimes involve a hydrolysis A and C are both large polymers DNA ligase 2.