BCHM 307 1st Edition Lecture 12 Outline of Last Lecture I Mass Spectrometry A Definition of Ionization Source B Definition of Mass Analyzer C Definition of Detector II In Gel Protease Digestion III Unknown Protein Analysis A Peptide Mass Fingerprinting B Tandem Mass Spectrometry IV Enzymes A Definition of Enzyme B Definition of Substrate V The Two Enzyme Model Outline of Current Lecture I Enzyme Reaction II Enzyme Rate Equation III Michaelis Menten Plot A Definition of Enzyme Velocity B Velocity Equation C Michaelis Constant Current Lecture The way that enzymes interact with substrates can be shown by the following equation E S ES ES EP E P E is the enzyme S is the substrate ES is the enzyme substrate complex ES is the enzyme transition state complex EP is the enzyme product complex and P is the product The place where the substrate binds is called the active site The active site is like a pocket in the enzyme which is made by protein folds Substrates can use hydrogen bonding hydrophobic interactions and ionic interactions to promote binding to the active site The various complexes mentioned above represent a mixture of enzyme and substrate The ES is neither substrate nor product but a transition point Once the product is formed the enzyme will release it The reaction can be simplified to A B P where A and B are two These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute reactants and P is the product formed after the reaction has been catalyzed by an enzyme The rate of the reaction is a function of change in time It can be defined three different ways shown below based on the decreasing amount of reactant or increasing amount of product A t B t P t The quality of the enzyme activity or assay can be determined through various methods It can be based on the disappearance of the substrate or appearance of the product The change in the gain of a product loss of a substrate over time is called the velocity Velocity of a reaction that is catalyzed by an enzyme depends upon the concentration of the substrate It should be noted that it is not over a change in time This data can be plotted in what is known as a Michaelis Menten plot This graph will give you a hyperbolic shape The initial velocity is plotted on the y axis The concentration of the substrate over time is plotted on the x axis The velocity will increase as the substrate concentration increase until the enzyme is fully saturated The graph will level off at this point and the added substrate will not change the velocity of the reaction During this whole process the amount of enzyme will not change Vmax x S It is based on the simplified Km S version of the enzyme reaction where K1 and K3 are forward rates and K2 is the reverse rate K1 The Michaelis Menton equation is V K3 E S ES E P This equation looks at the initial rates when P is close to 0 K2 For the above velocity equation V is the velocity at a given substrate concentration S Vmax is the maximum velocity seen when the enzyme is fully saturated called the zero order reaction Km is called the Michaelis constant and can be found by the following K 2 K 3 E S which is approximately equal to A low Km indicates a high affinity K1 ES for the substrate Km
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