NHM 361 ENZYMES on 9.19
NHM 361 ENZYMES on 9.19 NHM 361
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This 3 page Class Notes was uploaded by Vanessa Notetaker on Wednesday September 21, 2016. The Class Notes belongs to NHM 361 at University of Alabama - Tuscaloosa taught by Amy Cameron Ellis in Fall 2016. Since its upload, it has received 2 views. For similar materials see Nutritional Biochemistry in Nutrition and Food Sciences at University of Alabama - Tuscaloosa.
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Date Created: 09/21/16
NHM 361 Lecture on Enzymes 9/19 Enzymes Proteins that act as catalysts for chemical reactions ALL enzymes are PROTEINS As catalysts, enzymes increase the rate of chemical reactions but, they are not consumed or destroyed by the reaction o Enzymes can be used over and over without being changed They work by lowering the activation energy required for a reaction to proceed o Do not make a reaction that wouldn’t succeed otherwise, they simply speed up a reaction that would already occur Recall: Carbonic anhydrase is the enzyme complex in Red Blood Cells that is critically important in gas exchange and changes to bicarbonate Enzyme Nomenclature Most enzymes end in the suffic “ase” Often named for the substances they act on and the reactions Kinase o Any group of enzymes that catalyze the transfer of a phosphate group from a high energy donor to a substrate o Addition of phosphate group to an organic molecule is called phosphorylation Phosphatase o Group of enzymes that catalyze the removal of a phosphate group o Dephosphorylation Enzyme Specifcity Absolute Specificity- Enzyme only acts on ONE and ONLY ONE substrate Relative Specificity- Enzye able to act on SEVERAL substrates that are structurally similar Cofactors Cofactor is a molecule or ion required by an enzyme for catalytic activity Coenzyme is when a cofactor is an organic substance Enzyme- Substrate Complex Apoenzyme-the protein portion of the enzyme that is separable from its cofactor Holoenzyme- a complete enzyme- cofactor complex Apoenzyme + Cofactor= Holoenzyme Mechanism of Enzyme Action Enzyme action begins with a substrate binding to the active site Active site is the region on the enzyme where the substrate binds o The binding of substrate and enzyme is the enzyme-substrate complex The lock and key theory states that the enzyme and substrate fit into each other like a lock and key o Enzyme=lock o Substrate=key Induced fit theory is the updated version of the antiquated lock and key theory o The active site can be partially flexible o Conformation of the enzyme changes to accommodate substrate binding Factors Affecting Enzyme Activity Enzyme Concentration o The more enzyme the higher the rate of reaction Substrate Concentration o The more substrate the higher the rate of reaction until all the enzymes become saturated and the maximum rate is reached Temperature o There is an optimal temperature where each enzyme can function o Too high or too low denatures the enzyme pH o Optimum pH range exists also o Most enzymes have an optimum pH or 7.4 Pepsin functions best at pH or 2 (stomach acid) Enzyme Regulation Enzyme inhibitor is any substance that decreases the activity of an enzyme o Irreversible inhibition occurs when a substance covalently bonds to an enzyme rendering it permanently inactive Cyanides and heavy metals o Reversible inhibition involves non-covalent bonding of an inhibitior Competitive inhibitor competes with substrate for binding at an active site o Have similar structure to substrate o Malonate, ethanol Noncompetitive inhibitor binds to the enzyme at a location other than the active site and changes the shape of the active site so substrate can no longer bond o Isoleucine Allosteric regulation is when substances bind to enzymes at locations other than the active site to upregulate or downregulate enzyme activity o Upregulation is caused by activators o Downregulation is caused by inhibitors Feedback inhibition is a mechanism of an enzyme regulation in which accumulation of the end product of a biochemical pathway inhibits activity of the first enzyme in the pathway Enzyme and Help Zymogens or proenzymes are active precursors of an enzyme Some enzymes are stored as inactive enzymes and are released when needed and activated at location where the reaction will occur Trypsin that digests protein in the small intestine is created in the pancreas but, is inactive until it is released into the stomach and is exposed to the acidic solution o When trypsin is activated too early it causes pancreatitis where it eats the lining of the pancreas because it is digesting that protein instead of the protein in the stomach Genetic Control The Synthesis of All Proteins including Enzymes is dictated by genes
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