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what does an enzyme do to the rxn rate inc the rate what does an enzyme do to the activation E lowers it which step has the highest activation E the rate limiting step (in a multi-step rxn) what does G6Fd deficiency cause? causes hemolytic anemia due to exposure to oxidative stress what does a heme syn enzyme deficiency cause? porforiya what is the measurement of enzyme activity in blood and tissues used for? diagnose certain disease can drugs target specific enzymes? yes what enzyme does nitroglycerin target? guanalatecyclase what enzyme does aspirin target? cyclooxygenase I and II what happens if something happens to the enzyme conformation? lose enzyme activity what do some enzymes req? what helps them? co-factors what is holoenzyme composed of? Apoprotien+ cofactor=holoenzyme has complete enzyme activity what is an apoprotien? protien portion of an enzyme what is a cofactor? non protein chem grp What metals do some enzymes req? Zn2+ Fe Cu what metal does carbonic anhydrase req? and what for? zn carbonic anhydrase: CO2+H2o--->carbonic acid what metal does cytocrome c oxygenase req? and what for? Fe and Cu O2-->h2O how can enzymes be modified? (4) phosphrylation, methylation, glycosylation, adenylation what is adenylation? when glysine and arginine are attached w AMP how does pH affect enzyme activity? enzyme has optimum activity depending on the env where it is used. ex: pepsin (stomach pH 1-2) optimum pH for pepsin is 1.6 if go to small int (neutral pH), pepsin will lose its activity what is proteolysis? ex of how it affects enzyme its when u have a zyogomen that needs to be activated. so have to remove AA from zygomen ex: trypsinogen has AA removed to make trypsin what does enzyme kinetics do? tells mechanism of rxn, nature of inhibitor (if one is being used) what factors affect rxn rate? substance conc presence of inhibitor what is Vmax? when rxn rate plateaus bc substrates have taken up all active binding sites, meaning it is saturated what does Km =? its Michaeli's constant =1/2 of Vmax V knot= Vmax*[S] vo= _________ Km + [S] rearrange Vo making Km=1/2Vmax Km=[S] Whats does Michaeli's menton equation assume? (3) -ES complex is at steady state -All enzymes go to ES complex (no enzyme left over) -w/ all enzyming going to ES complex, will get Vmax what influences Km values? (3) Ph, temp, [salt] can two enzymes catalyze the same substrate? yes can one enzyme catalyze two substrates? yes if u have 2 enzymes that metabolize the same substrate but 1 enzyme has a higher Km, what does that mean in terms of substrate being metabolized by the enzymes? when u have a rxn proceeding at a rapid rate w low [ ] of substrate, the low Km form of the enzyme is responsible for catalyzing it do allosteric enzymes obey Michaelis-menton kinetics? no what is an allosteric enzyme? an enzyme w multiple subunits and active sites what types of cure do allosteric enzymes obtain? sigmoid curve binding of substrate is cooperative with what type of enzymes? allosteric what type of subunits do allosteric enzymes have? catalytic and regulatory subunits. what binds to regulatory subunit of allosteric enzyme? allosteric modulator what binds to catalytic subunit of allosteric enzyme? substrate what do allosteric modulators do to allosteric enzymes? bind by reversible, non-covalent bond and cause change in conformation of enzyme. therefore, affects affinity for substrate to bind what does a positive allosteric modulator do to enzyme activity? to the sigmoid curve? increases enzyme activity; conformation change will inc enzyme affinity for substrate shifts curve to the left what does a negative allosteric modulator do to enzyme activity? to the sigmoid curve? decreases enzyme activity; conformation change will dec enzyme affinity for substrate shifts curve to the right what rxn does glycogen phophorylase catalyze? glycogen into glucose 1-phosphate what type of modulator does high glucose levels have? negative what type of modulator does high Amp levels have? positive meaning the body has low E what type of inhibitor is methotrexate? reversible what is a reversible inhibitor? one w a weak bond b/t inhibitor and enzyme causes dissociation what type of bond does an irreversible inhibitor have? strong covalent bond what type of inhibitor is aspirin? irreversible what type of inhibitor is penicillin? irreversible what type of inhibitor is fluorouracil? suicide inhibitor what does aspirin bind to? cox 1 and 3 and acelylate serine what does penicillin bind to? covalently binds to transpeptidase thus prevent the syn of bac cell wall what type of inhibitors are most drugs? reversible competitive inhibition drug examples what do they inhibit? lipitor inhibit HMG CoA reuctase non-competitive inhibition drug examples what do they inhibit? deoxycycline (anti-biotic) inhibits collagenase in bac what is collagenase needed for? protein syn un-competitive inhibition drug examples what do they inhibit? herbicide glycophosphate (round up) inhibits EPSP synthase what is EPSP synthase used for? aromatic AA syn for protein syn which types of inhibitions are reversible? competitive, non-competitive, un-competitive which types of inhibitions are irreversible? mechanism based (suicide) inhibition how can competitive inhibition reversed? by increasing the substrate [ ] this affects Km; not Vmax can either have ES or EI complex what type of inhibition does anti freeze deal with? competitive what does anti-freeze contain and what is it metabolized to? contains methanol that is metabolized to formaldehyde (toxic) by the liver w alcohol dehydrogenase what does anti-freeze do to a person? can become blind bc eyes are very sensitive to formaldehyde how do u treat anti-freeze poisoning? w high [ ]s of ethanol by IV over several hrs why do u treat anti-freeze poisoning w ethanol? bc it is metabolized by the same enzyme to form acetalaldehyde (non toxic), the methanol will then be filtered by the kidney and excreted in the urine what does the Ki value show? tells how potent the inhibitor is. the lower the Ki value, the more potent the inhibitor is Ki value= Km (no inhibitor) Ki= __________________________ *[I] (Km w inhibitor)-(Km no inhibitor) what axis does the competitive inhibitor intersect? why? y-axis bc it affects Vmax what type of complex does non-competitive inhibition have? ESI does increasing the substrate [ ] overcome inhibition for a non-competitive inhibitor? no what affect does a non-competitive inhibitor have on Km and Vmax? Km stays the same, but Vmax decreases what axis does a non-competitive inhibitor intersect? why? x-axis b/c there is no change in Km but Vmax decreases when can an uncompetitive inhibitor bind? can only bind after substrate binds b/c when substrate binds, it exposes site for uncompetitive inhibitor does increasing the substrate [ ] overcome inhibition for an uncompetitive inhibitor? no what affect does an uncompetitive inhibitor have on Km and Vmax? they both decrease what axis does an uncompetitive inhibitor intersect? why? it doesnt intersect b/c they are parallel lines what is mechanism-based (suicide) inhibition? inhibitor metabolite covalently binds to enzyme either to the protein or prosthetic group what happens if a suicide inhibitor binds to the prosthetic group? the enzyme is catalytically inactive what happens if a suicide inhibitor binds to the protein? results in lose of fxn due to irreversible alteration of struc