3 holo enzyme (active enzyme) active siteNon-protein part can be a cofactor or a coenzyme. It is the part which makes an enzyme active.non-protein partproteinapoenzymeCofactorinorganicex: zinc, iron, potassium, copperCoenzymeorganicex: vitamins, NAD, FAD, NADP+@
4 Enzymes… Are made up of proteins Simple Enzymes: only made up of proteins.Complex Enzymes: are made up of proteins + non protein part
5 Structure of Enzymes… Two major parts: Protein part: Apoenzyme : made up of protein.not catalyze the reaction by itselfhas to interact with non protein partNon- protein part :Coenzyme: made up of organic molecules (vitamins)Cofactor: made up of inorganic molecules (K, Ca )++
6 Structure of Enzymes… Lock and key Substrate:The molecule which enzyme acts onActive site: Specific region on the enzyme that substrate bindsEnzyme –Substrate ComplexLock and key
7 One apoenzyme works with only one coenzyme or cofactor Enzymes are not changed or used upThe same enzyme works for the forward and reverse of the reactionsLipid +H2O Fatty Acids +GlycerolLipase
8 Properties of Enzymes Specificity: Enzymes work with only one type of substrateFinal molecule of the reaction is productNot used up, destroyed at the end of reactionCan be used over and over until destroyed by other factors (heat)
9 Properties of Enzymes… ReversibilityCatalyze reactions for forward and reverse directionsNot determine directionRatio of equilibriumOnly digestive enzymes catalyze reaction in one wayNamingAccording to molecules they act :-aseExp: Lipase, AmylaseorPepsin, TripsinAccording to type of reaction catalizing.
10 Properties of Enzymes… The exact point of effectSurface of areaWider surfaceGreater rate of reactionSpeedSpeed up reactionWithout enzyme breaking down takes more time
11 Properties of Enzymes… Work in Teamsthe product of one reaction catalyzedThe substrate for another enzymePlace of synthesisApoenzyme part is protein, so synthesized in ribosomes just like proteinsGene destroyedEnzyme not synthesizedCell diesMaltaseAmylaseStarchGlucoseMoleculesMaltoseMolecules
12 Enzyme-substrate complex (temporary) There are two models that provide explanation to enzyme action:Lock and Key Model: The substrate(s) fits exactly into the active site of the enzyme.@E SE – SE PEnzymeSubstrateEnzyme-substrate complex (temporary)EnzymeProduct
14 2. Induced Fit Model:@In this model, the enzyme has no rigid shape. Instead the enzyme changes shape slightly as the substrate enters the active site. Once it has changed shape, the enzyme fits tightly around the substrate As the enzyme embraces the substrate it can weaken the chemical bonds in the substrate, which helps the reaction to proceed.The enzyme changes shape slightly to grasp the substrate at the active site.
15 Characteristics of Enzyme Action: @Small amounts of an enzyme can cause the reaction of large quantities of substrate.- The time needed for an enzyme-substrate complex to form and a reaction to occur is very short.- A simple enzyme molecule can catalyze thousands of substrate reactions in a second.
16 2. Enzymes enable cell reactions to take place at normal temperatures. @enzyme activityOptimum temperature for many enzymes (about 36oC)temperature (oC)
17 At OoC, enzymes do not function although their structure is not changed (they are not denaturated). The temperature at which an enzyme is most effective is called the optimum temperature of an enzyme. At their optimum temperature values enzymes work best.At higher temperatures (like 55oC) enzymes are denaturated and they lose their properties. So they cannot catalyse a reaction.
18 3. Each enzyme works best at a certain pH. Optimum pH for pepsinenzyme activityOptimum pH for many enzymesOptimum pH for trypsinpHThe effectiveness of an enzyme depends on the pH of medium.Each enzyme works at different pH values.
19 5. Some enzymes need substances called activators in order to function. Activators are coenzymes or cofactors.6. Some enzymes function inside the cell, others act outside of the cell. Ex: pepsin
20 7. Inhibitors stop or slow down the activity of enzymes. Antibiotics, pesticides, herbicides, heavy metal ions (Pb+2, Hg+2, Ag+2 ), CO, snake and scorpion poisons, CN, CuThey slow down or stop the activity of enzymes
21 InhibitorsCompetitiveNon - CompetitiveThose inhibitors compete with the normal substrate in attachment to the active siteThey have an influence on the protein part of the enzyme apart from the active site
23 Enzyme activityenzyme + activatorenzymeenzyme + inhibitorConcentration of inhibitor or activator
24 8. Amount of water affects the enzyme activity. If a medium contains less than 15% water, then the enzyme activity stops.9. Substrate surfaceEnzyme action begins from the substrate surface.Therefore, increasing surface area of substrate increases the rate of recation until a maximum rate is reached.rate of reactionsurface area