Lecture 10 Student Notes-Intro to Enzymes PDF

Enzymes backtooriginalstate Definition and Characteristics MightchangebutMUSTgo Proteins that act as _________ (increase reaction rates without being used up). Ca...

Enzymes backtooriginalstate Definition and Characteristics MightchangebutMUSTgo Proteins that act as _________ (increase reaction rates without being used up). Catalyst 295 Most enzymes make __________________ or breakcovalentbonds ________ Some enzymes are transporters and use chemical energy (e.g. split ATP). Only specific reactions are catalyzed by each enzyme: Enzymes (as a group) can catalyze a wide variety of reactions. According to the type of reaction they catalyze, enzymes have been grouped into __________major six classes. aroup remove S Cofactors, Coenzymes and Prosthetic Groups A _______________ Cofactor is a non-protein chemical compound or metallic ion that is required for an enzyme's activity as a catalyst. Cofactors can be divided into two types: mins A. ____________ B. __________- coenzy complex organic molecules Inorganic Ions requiredfor f deficiant Fish ionenzyme ontwork The metal cofactors are obtained in the diet, and since many of the organic cofactors cannot be synthesized by humans, they are derived from vitamins. 1  Coenzymes are further divided into two types. A. Prosthetic _______________- a coenzyme that is Group permanently bound. j jijsÉÉe butchangebackbydifferentenzyme changed B. _____________- transiently bound to protein. NOTE-Co-substrates are released from the enzyme at some point, but rebind later so another reaction can occur. ______________ Apoenzyme + cofactor (or coenzyme, prosthetic group) = _____________ holoenzyme is e confiteinitive pinetzyme is How do enzymes accomplish catalysis? First, an enzyme must bind the _____________s). Substrate 1 Binding of substrates and catalysis occur at the _______________. Active Site This is facilitated by multiple non-covalent interactions (shape and chemical complementarity of active site and substrate(s)). The active site is made up of just a few AAs out of the total polypeptide chain = active site residues or _______________. CatalyticAAs Consider a hypothetical enzyme breaking a stick (a “stickase”): Energy fa Before the stick is broken, it must first be bent =Transition _______________ state tsf scantn m'e For any reaction energy is required to get to the transition state of the reaction ‡ = Activation _______________, Energy ∆G. Higher Slower The ____________ the activation energy, the _____________the reaction 2 If the binding pocket is complementary in structure to the substrate (the stick), it will stabilize the substrate. Bending is impeded by the magnetic attraction between substrate (stick) and enzyme (stickase). A pocket complementary to the TS helps to destabilize the stick= reduces ___________ ‡ the activation energy (∆G ) = ___________________ Speeds ran up É The binding energy of the magnetic interactions compensates for the increase in free energy required to bend the stick. How do enzymes increase rxn rates? They bind the Transition ___________________ State TS better than either substrates or products o If enzyme were to stabilize (bind) the substrates too much  the reaction would not proceed. o If enzyme were to stabilize (bind) the products too much  the products would not be released. Stabilization of the transition state occurs through multiple non _______________interactions colvalent between the (new) transition state and the enzyme. The active site is chemically ___________ and ____________ complementary to the transition state of thesterically reaction. 3  cnet.ee Induce fit model: The conformation that best fits the transition state may not be present initially. Enzymes can _______________to changeShape allow optimal binding of the transition I onceenzyme state. Position During substrate binding, catalysis and lowergtivation release of products the enzyme adopts different conformations. https://www.youtube.com/watch?app =desktop&v=V8TOWTp71tE Thermodynamics of enzymes Enzymes accelerate reactions, but like all catalysts, do not change the ____________________ (concentrations of substrates and products. Thermodynakisnfgynilileri.tl productEx Ifgivena ofproductcanmake5sofproduct The equilibrium is determined by ∆G of the reaction (∆G’ in Biochemistry). Enzymes do_______________the not ∆G (∆G’) of the reaction. change ∆G = ∆H – T∆S 1 If ∆G _______________ the reaction occurs spontaneously. If ∆G _______________ more the reaction is not favored (requires energy). 0 t If ∆G _______________ 0 the reaction has reached its equilibrium. Specificity of Enzymes As is the case for many protein-ligand interactions, multiple weak (noncovalent) interactions add up to provide the ∆G of binding. If the interactions are complementary to a specific substrate (or substrates), other molecules will lack these interactions= Substrate _______________ specificity Summary Multiple weak noncovalent interactions occur between the substrate(s) and the enzyme. phtiei.is citic The binding energy contributes to ____________ and Catalyst _____________ Specificity These weak interactions are optimized for the reaction'sTransition _______________ State Ts 4  Enzymes Learning objectives Upon learning the content of this lecture you should be able to 1 Define the term “enzyme” and the chemical nature of the majority and a minority of enzymes. 2 List the main classes of enzymes according to the international classification of enzymes. 3 Define the terms “cofactor”, “coenzyme”, prosthetic group”, “apoenzyme”, and “holoenzyme.” 4 Explain the relationship between coenzymes and vitamins. 5 Explain how enzymes achieve catalysis using the using a hypothetical model enzyme (“stickase”). 6 Explain in chemical terms how an enzyme active site needs to be constructed to achieve both substrate binding and catalysis. 7 List which thermodynamic parameters are changed in enzyme-catalyzed reactions compared with un-catalyzed equivalent reactions. 8 Explain the difference between ∆G’ and ∆G°’. Explain how both are related to the concentrations of substrates and products during an ongoing enzyme reaction and at equilibrium. 9 Define the term “induced fit”. 1