Class Note for MIC 205A at UA
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Date Created: 02/06/15
Microbial Metabolism Enzymes What is metabolism I The sum ofchemical reactions within a living organism mu en icm mm quotmm Why do we need to know about microbial metabolism I Metabolism is the basis ofall life notjust microbes I Metabolism forms the basis of all forms of microbiology 39om environmental microbiology to medical microbiology I lfyour interest is in human health knowledge ofmetabolism forms the basis of antibiotic therapy Some antibiotics interfere with metabolic reactions Catabolic and Anabolic reactions I Catabollsm I The breakduvvn er cumplex urganl mulecules lnte slmpler mulecules I Generally hydrulytl I Exergunl pruduce energyyenergy stared ln enernleal bands is released I Anabollsm I The synthesls er cumplex urganl muleculesfrum slmpler mulecules I Generally dehydratan synthesls reactluns release water I Endergunl cunsume energy Role of ATP in metabolism I ATP adenoslne tnphosphate stores the energy generated by catabollc reactlol39ls and makes ll avallable for anabollc reactlol39ls Enzymesthe driving force of metabolic reactions I An enzyme is a biological catalyst that speeds up chemical reactions is the cell I Increase the rate ofa chemical reaction 10510m times to the speed of life I Speci c for a particular substrate and reaction I The unique threedimensional shape of an enzyme allows it to recognize its substrate How do enzymes work I By decreasing the activation energy the 7 energy required to initiate a chemical reaction I Enzymes have an active site at which only specific reactants or substrates are positioned for various interactions 3 S J J t i quotWNIMM Enzymesubstrate interaction Sthlll 39lt 5i thMn W Turnover number I Enzymes participate in chemical reactions butare not consumed by them can function over and over again I An enzymes speed or turnover number is the maximum number of substrate molecules an enzyme molecule can convert to product each second I Enzyme speeds can range over several orders of magnitude but are characteristic of a particular enzyme I Examples I DNA polymerase DNA synthesis E 15 Enzyme components I Simple enzymesentirely protein I Conjugated enzymes consist of I Apoenzymethe protein component I Cofactornon protein component eg Mg2 or Ca2 ions lf cofactor is an organic molecule it is called a coenzyme I Apoenzyme cofactor Holoenzyme I In the absence of the cofactor the apoenzyme is inactive Cramquot mayr lktnii in 39 7 mm keenrm c39oIlM I Catalase breakdown of H202 gt 20000 Coenzymes 55921 Important coenzymes in cellular I Can act in catalysisbyacceptinga metabolism chemical group from one substrate Wm l and transferring it to another C substrate Some act as electron carriers Many are derived from vitamins Examples I vitamin Becoenzyme in amino acid metabolism I Folic acidcoenzyme in the synthesis of nucleotides I Nicotinamide adenine dinucleotide NAD I NAD is involved in catabolic reactions I Nicotinamide adenine dinucleotide phosphate NADPt I NADP is involved in anabolic reactions I Both NAD and NADPH are derivatives of vitamin B1 niacin and they both function as electron carriers Other key coenzymes I The llavin coenzymes I Flayin mononucleotlde FMN and llale adenine dlnucleotlde FAD Derivatives ofvltamll i E32 riboflavin I Also act as electron carriers I Coenzyme A Derivative ofvltamll i E35 pantothenlc acid I important roles in fat metabolism and the TCA cycle Naming enzymes Class 17 asequotl Wm M chemsz reactinn Oxmnreduclase m eeamns lmnsierase lransier mvunmmnzl umuns such as an amlnn nr 2 rlhnsrlhale mur Hyerniase Cleaves hnnes nn mniemies with the zeenmn m waer thy rnhslsl ste Reman nr zeenmn n1 nrnurls n1 alums wnhnul hy rnWss Isnmezse Rmrmnnemml n1 alums within a mnieeuie Lmase Jnlnlnn Iwn mnieeuies tuslnu enemy mm the breakean n1 Arm Factors affecting enzymatic activity nele atcnemical veactians nus enzymes nave a pH my suhmg Dancemmym increases wtn temperature Dmmium mm m am By mm mm ne enzyne is Said ta relevatmn shave a certain enanees in pH can muse temperature reduces result in alteraimnsintne be sawed enzymatic aemyeeem 3Dstm uve mtne enzyme We may mums denatuvatian m the enzyne leading ta denaturatmn 2mm 32 m WM Exo and endoenzymes Exuenzvmes Actiyeumslde Eneeenzymes tnecell Must metabullc Eveakduwn e1 W Enzymesave nutvlemstnat are M enduenzymes tun lame tn enter me cell seme plavamle in msease e an strewnkinasEy nnnsnnunpase 0 new New Control of metabolic pathways I Metabolic pathways are controlled at the level of their enzymes I Control of enzymes Synthesis Activity Production of enzymes in the cell Enlvmes an be Praduced at eansam levelsintne eeu 0R lnew meean can he veemelee in yeseansem substrate av madam canuemvatmns Enzyme Inhibitors I An effective way to control the growth of bacteria is to control their enzymes I Certain poisons such as cyanide arsenic and mercury combine with enzymes and inhibit their activity I Enzyme inhibitors can be classed as Competitive inhioitors Noncompetitive inhioitors Competitive inhibitors Fill the active site and compete El with substrate Simiiar in shape and chemicai structure to the substrate Dues nut undergu anv reaction tn rorm products Mav bind reversioiv ur irreversioiv e e ilrihibnian atmlicacid Wmhess bv sAltanilariiide Noncompetltlve Inhibitors I li39iteractvvith a site other than the active site allosteric orregulatorv site I Binding ofthe ii39ih bitor causes a change inthe shape or the active Site making it nonfunctional aiiostencinh oition Mav oino revers oiv or irreversoiv Enzyme Repression I The endproduct ofthe reaction signals back to the DNA to turn off expression ofthe gene I Prevents the cell from wasting energy The Cell s Energy Machine
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