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Clemson BCHM 3050 - Mechanisms of Enzyme Regulation

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BCHM 3050 1st Edition Lecture 12 Outline of Last Lecture I. How does liquidy syrup inside candies form?II. Substrate Concentration has the Greatest EffectIII. Initial Velocity is FastestIV. Importance of Vmax and KmV. Significance of KmVI. Experimental Determination of Vmax and KmVII. The Michaelis-Menton EquationVIII. Lineweaver-Burk PlotsOutline of Current Lecture I. General Mechanisms of Enzyme Regulation II. Three Main Types of Inhibitorsa. Competitiveb. Non-competitivec. UncompetitiveIII. Designer Drugs for AIDSIV. Covalent Modification of EnzymesV. Allosteric Regulation of EnzymesVI. Other Factors that Regulate Enzyme ActivityCurrent LectureThese 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.I. General Mechanisms of Enzyme Regulation a. Genetic Regulation i. Majority of enzymes are proteins, so they are regulatedii. Enzyme activity is controlled by genetics (DNA)iii. DNA decides how much enzyme will be available, when it will reactb. Substrate vs. Product Availabilityi. Can tip the balance towards the product by altering the amount of enzyme present or the concentration of substrateii. Add inhibitors to decrease enzyme activity or recognize the presence of an inhibitor and take it away to increase rate of reactionc. Mechanisms of Inhibitioni. “Suicide Inhibitors” are those that not only bind to the active site of an enzyme, but more importantly react with the active site to become “permanently bound” to the enzyme.ii. Modern “rational drug design” uses this strategy in making new drugs.iii. Penicillin is a good example of a suicide inhibitor (i.e. it inhibits transpeptidase from building bacterial cell walls).iv. Inhibitor can directly take over the enzyme, form an Enzyme-Inhibitory-Substrate complex à gets very low productsv. Inhibitors come and go, but this is reversible; so eventually you get a product II. Three Main Types of Inhibitorsa. Competitivei. Competitive Inhibitor – looks very similar to the substrate so it competes with the substrate to try to bind to the activation site and block out substrateii. If Malonate binds to the active site à the enzyme changes in shape à inactivating enzymeiii. Competitive inhibitory causes more substrate needing to be addediv. Put in more substrate to get the same product of the reactionv. Km increases in the presence of an inhibitor à which means you need much more of the substrate to achieve the same level of affinityvi. Vmax is not alerted by competitive inhibitorb. Non-competitivei. Non-Competitive Inhibition – doesn’t bind to active site, doesn’t affect Km, and reduces Vmaxii. This inhibitor is more permanent than competitive inhibitors; not reversiblec. Uncompetitivei. Un-Competitive Inhibitor – binds only to the enzyme substrate complex, lowers both Km and Vmaxii. Km decreases, but velocity also decreasesIII. Designer Drugs for AIDSa. The HIV virus is a complex enveloped or coated virus that causes AIDSb. Targeting the Protease enzymec. Original genetic material is RNA, rather than DNA, in the HIV virus à uses reverse transcriptase, single stranded RNA is easier to manipulated. Send inhibitors to enzyme protease to try to target the viruse. Aspartate protease simply means that aspartic acid (two residiues) in the active site are involved in proteolysis.f. Inactivate the protease à not allow the virus to continueg. Protease was a drug targeth. Protease breaks the bond between Tyr and Proi. Can now design an inhibitor against the protease to inhibit the enzyme functionj. Inhibitor is blocking the active site of the proteaseIV. Covalent Modification of Enzymesa. Covalent Modification – the (reversible) attachment of a functional group onto a protein or enzyme via a covalent bondi. Very few amino acids are in inhibited this wayii. Enzymes of glycogen metabolism (storage or breakdown) are regulated byphosphorylation/dephosphorylation.iii. Removing disulfide bond between cysteines à inactivates enzymesV. Allosteric Regulation of Enzymesa. Allosteric – includes non-competitive and uncompetitive inhibitors and activatorscan be allostericb. Allosteric means “other site”c. Activator – curve becomes more hyperbolic and shift to the leftd. Inhibitor – curve shifts to the rightVI. Other Factors that Regulate Enzyme Activitya. Availability of co-factorsi. Metal ionsii. Co-enzymesiii. pHiv.


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