Enzymes 1.7 & 3.3

Enzymes biological catalysts speed up chemical reactions without being consumed usually proteins with tertiary or quaternary structure (Image from: http://www-news.uchicago.edu/releases/06/061011.ied.shtml) FYI: This enzyme is the insulin-degrading enzyme, control of which might help to cure Alzheimer’s disease.

Enzyme Action enzymes bind to specific reactants called substrates substrates bind to active sites on enzymes, forming the enzyme-substrate complex

Enzyme-Substrate Complex (Image from: http://kentsimmons.uwinnipeg.ca/cm1504/energy.htm)

Induced-Fit Model in the “induced-fit” model, the enzyme alters its shape to better “fit” substrate contrast with the “lock and key” hypothesis (Image from: http://chsweb.lr.k12.nj.us/mstanley/outlines/enzymesap/Enzymesap.htm) Interactions between functional groups of enzyme & substrate cause enzyme to alter shape to better fit substrate

Example: Sucrase Image from: http://awesomebiology.wikispaces.com/Enzymes

What reactions do these enzymes catalyze? lactase breaks down lactose (sugar found in milk) ATPase breaks off a phosphate group from ATP, resulting in ADP + an inorganic phosphate + energy amylase breaks down starch (in saliva & intestine)

What about this one? ATP synthase synthesizes ATP from ADP and inorganic phosphate

Cofactors and Coenzymes some enzymes require cofactors to function as catalysts cofactors are non-protein molecules or inorganic ions coenzymes are organic cofactors Cofactors: Zn, Fe ions, etc. Coenzymes: NAD, FAD, CoA, etc. 9

Cofactors http://www.abc.net.au/science/articles/2010/10/13/3037285.htm 10

Homework (p.57) #3 What is the functional role of a coenzyme or a cofactor in an enzyme-induced reaction? Give an example of an enzyme that requires a cofactor or coenzyme.

Factors Affecting Rate of Enzyme Activity substrate concentration enzyme concentration temperature pH Increasing the substrate concentration increases the reaction rate to a certain point. Once the enzymes are saturated with substrate, the concentration of enzyme becomes the limiting factor. Protein (enzyme) folding depends on interactions between amino acid side (R) groups, some that are acidic or basic. Each protein (enzyme) has an optimal pH at which they fold correctly. Temperature – At high temperatures, enzymes become denatured and don’t function. At low temperatures, enzymes are too rigid to catalyse a reaction. Enzymes usually function best at body temperature (37C in humans).

Homework (p.57) #5 How does the rate of reaction change as a result of each of the following factors? (Support your answer with a graphic representation of the enzymatic rates.) enzyme concentration substrate concentration temperature pH

Homework (p.57) #10 Why is it important for the human body to maintain a proper temperature and a proper pH at all times?

Enzyme Regulation 15

Competitive Inhibition 16

Competitive Inhibition competitive inhibitors have a similar structure to the substrate bind to the enzyme’s active site and block the substrate from binding 17

Irreversible Inhibitors Many drugs & pesticides act as irreversible inhibitors of enzymes cyanide (inhibits key enzyme in cellular respiration) antibiotics (inhibit bacterial enzymes)

Allosteric Regulation some enzymes have allosteric sites allosteric regulators either inhibit or stimulate an enzyme’s activity 19

Allosteric Regulation http://julieteaslickby411.blogspot.com/2011/04/innervation-of-penis-and-structure-of.html

Allosteric Regulation 21

Allosteric Regulation allosteric activators promote the action of the enzyme allosteric inhibitors prevent the action of the enzyme (i.e. noncompetitive inhibition) 22

Homework (p.57) #6, 8 Describe noncompetitive inhibition. Provide an example to support your answer. Describe the different effects of an activator and an inhibitor on an allosterically regulated enzyme.

Feedback Inhibition often used to regulate multi-step metabolic pathways the product of a pathway usually acts as an allosteric inhibitor of the first enzyme of the pathway http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter8/animations.html# 24

(Image from: http://classes. midlandstech 25

Commercial Uses of Enzymes cheese lactose-free dairy products corn & wheat syrup sweeteners etc. (Image from: http://housewares.hardwarestore.com/35-176-laundry-detergents.aspx) Starch-processing into glucose through enzyme-catalyzed hydrolysis Cheese manufacturing involves enzymes called proteases (rennet) and lipases Dairy products without lactose. Detergents often contain proteases and amylases to remove protein and carbohydrate stains.

Homework (p.57) #11 You are making a gelatin dessert, but the directions tell you not to use fresh pineapple because the gelatin will not solidify. Pineapple contains an enzyme, bromelain, which is a protease. What effect does a protease have on a protein like collagen? Could you use cooked or canned pineapple instead? Explain your answer.

Homework (p.57) #12 Humans produce enzymes in the mouth, stomach, and small intestine that aid in the process of digestion. As we age, we tend to produce less of these enzymes. What effect could this have on digestion and nutrition?

Activation Energy (EA) all chemical reactions require an initial input of energy, called activation energy (EA) (Image from: http://drmccarthysciencehgms.blogspot.com/2010/03/endothermic-vs-exothermic-chemical.html) Recall collision theory from Grade 10 Science 29

Enzymes & Activation Energy 3.3

Enzymes and EA (Image from: http://www.glogster.com/glog.php?glog_id=10884793&scale=54&isprofile=true)

Activation Energy enzymes increase the rate of a reaction by lowering the activation energy (EA) How? 32

How is Ea reduced? weak bonds form between substrate and enzyme enzyme provides proper orientation of substrate(s) enzyme puts strain on bonds of substrate(s), making them easier to break 33

Animation Activation Energy & Enzymes: http://www.sumanasinc.com/webcontent/animations/content/enzymes/enzymes.html 34