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Dr. Chegwidden Biochem 04

Terms in this set (28)

1.Define enzyme
2. Similarities between enzyme and chemical catalyst(3 things)
3. Differences between enzyme and chemical catalyst(2 things)
1.Large globular proteins that catalyze chemical reactions in biological systems
2.-Accelerate the rate of reaction
-required in small concentrations compared to the amount of substrate converted
-Enzyme is left unchanged after reaction
3. -Enzymes are much more efficient
-Enzymes are much more specific and usually only act on one particular substrate
Why are enzymes so important?
The body modifies the activity of enzymes to control its chemistry
-Many processes in the body requires many steps > each step is catalyzed by an enzyme > this allow for many points of control
1.What is an active site?
2. How are substrate bind and catalysis achieved?
3. What would happen if there was a mutation at the active site?
1. The part of the enzyme where the substrate binds
2. it is achieved by interactions between substrate and specific amino acids in the active site
3. If a mutation occurs then the enzyme would be deficient
Lock and key model
1.Chymotrypsin
2.Trypsin
3.Elastase
Some degree of specificity
1.Cleaves peptide bonds next to bulky non polar side chains
2.Cleaves peptide bonds next to basic side chains
3.Cleaves peptide bonds next to small, non polar side chains
Induced fit Model
It works like putting a hand in a glove
- explains the high specificity for enzymes like creatine kinase
Coenzymes
1.What is it?
2. Can an enzyme require more than one coenzyme?
3. Where are coenzymes derived? How large are they?
4. Are Coenzymes specific to any one enzyme?
5. What are cofactors?
1. They are a non protein compound necessary for the function of an enzyme
2. Yes some enzymes require more than one
3. They are mostly derived from vitamins and they are smaller than enzymes(MW<1000)
4.No, they can assist a number of different enzymes
5. metal ions used to assist in catalytic processes
Memorize Coenzymes
Memorize Vitamins = deficiency
LIL'HOT
1. Ligase: bond formation via ATP use
2.Isomerase: isomerize
3. Lyase: Breaking apart a compound without the use of water
4.Hydrolase: Breaking apart using water
5. Oxidoreductase: transfer of electrons or hydrogen atoms
6.Transferase: transfer of functional groups
1.How is an Enzyme Quantitated?
2.Katal
3.Enzyme unit
4. Turnover number
1. By the enzyme activity (The conversion of substrate to product)
2. amount of enzyme to convert 1 mole of substrate to product in 1 second
3.amount of enzyme to convert 1 micro-mole of substrate to product in 1 minute
4. The rate of conversion of substrate to product when enzyme is fully saturated
Factors affecting enzyme activity
1. Concentration
2.Temp
3. pH
4.Substrate concentration
1. The more enzyme you add the more activity
2. Activity increases to a certain point and drops off (optimal temp)
3. More of a symmetrical bell shaped curve (optimal pH= 7)
4. michaelis menten plot
-At low substrate concentration (from 0 to Km): enzyme activity is proportional to the amount of substate added = straight line slope going up
-At high substate concentration (from Km up): Enzyme activity starts to level out until it hits a Vmax
1. enzyme Velocity equation
2. What does a small Km
1. V = (Vmax [S])/(Km + [S])
Irreversible inhibitors vs Reversible inhibitors
Irreversible inhibitors
- bind covalently
-as time goes on more enzymes are inhibited
- Overcome by making more enzyme
Reversible inhibitors
-Bind via weak interactions H-bonds, charge interactions, hydrophobic interactions
- Equilibrium with enzyme
-Overcome by dilution or dialysis
Irreversible Enzyme Inhibitors
1. Organophosphorus compounds
2.Malathion
3.Sarin
4.Asprin -Function?
a) what does it reduce?
b) What does it inhibit?
c) what conditions does it protect against?
d)How long does it last?
1. Covalently modifies the serine side of acetylcholinesterase thus inhibiting it > blocks transmission at the neuromuscular junction
2.an insecticide
3.Chemical Weapon
4. Non-steroidal anti-inflammatory drug (NSAID) that covalently modifies cyclooxygenase
-Cyclooxygenase helps turn Archidonic acid to prostaglandins, prostacyclin and thromboxane
a) Reduces inflammation (prostaglandins mediate inflammatory response)
b) Inhibits platelet aggregation(Thromboxane induces platelet aggregation)
c)Protects against Stroke and Myocardial Infarction in patients with Coronary Artery Disease
d) lasts 10 days because thats how long blood cells live
Gout
1.What is it? due to what?
2.What structures form in the joint space?
3. Where is it first presented and how long does it take to resolve?
4. What can chronic gout lead to?
5. Treatment?
1. Acute joint inflammation due to hyperuricemia (Excess Uric acid in the blood)
2.Needle like ureate crystals in the joint space
3. 1st MTP joint in the great toe, 3-10 days
4.Damage to joint cartilage
5. For acute symptoms: NSAID (indomethacin)
For longterm treatment: Allopurinol (Xanthine oxidase inhibitor)
Mechanism Based Enzyme inhibitor
1.Allopurinol
a) What does it inhibit? Its an analog of what?
b) What does it reduce? What does it treat?
2.Penicillin
a) what does it inhibit? What is this enzyme responsible for?
b) how does this inhibitor work?
1. a) xanthine oxidase, Purines
b) Reduces uric acid production, Gout
2. a) Inhibits transpeptidase, Responsible for synthesis of bacterial cell walls
b) It contains a strained peptide bond that resembles/mimics a transition state of the enzyme> is able to bind more tightly than substrates and products
Reversible Enzyme inhibitors
1. These inhibitors are at ________ with enzyme and are characterized by what value?
2. Good inhibitors vs Bad inhibitors
3. Competitive Inhibitor vs Non-Competitive Inhibitor
1. Equilibrium between Enzyme(E) and inhibitor(I) (E + I <> EI) , Ki which is Ki = ([E][I])/[EI]
2. Good inhibitors = Low Ki ... Bad inhibitors = High Ki
3. Competitive Inhibitor = km increases, Vmax stays the same
-Non-Competitive Inhibitor = Km stays the same, Vmax decreases
Reversible Enzyme inhibitors > Competitive > Sulfonamides
1. What do Sulfonamides inhibit and what does it compete with?
2.What is this enzyme involved in?
3. What does PABA make?
4. Was it the first anti bacterial agent?
1. Sulfonamides competitively inhibit dihydropteroate synthase in bacteria by mimicking PABA
2. Involved in the *synthesis of folic acid > which is required for nucleotide synthesis/replication
3. PABA synthesizes Folic acid (which is essential for nucleotide synthesis)
4. YES
Reversible Enzyme inhibitors > Competitive > Methotrexate
1. What does it inhibit? What does compete with?
2.What is this enzyme involved in?
3. What needs to happen to folic acid to be active?
4.What therapy is this inhibitor used?
1. It inhibits folate activation (from dihydrofolate reductase enzyme) by mimicking folic acid
2.Involved *Activating folic acid for Nucleotide synthesis
3.Folic acid must be activated to tetrahydrofolate in order to carry out its functions in nucleotide synthesis
4. cancer chemotherapy
Reversible Enzyme inhibitors > Competitive > Warfarin
1. What does it inhibit?
2. What is this enzyme involved in?
3. What is this inhibitor used for?
1. Coumadin(Warfarin) inhibits Vitamin K epoxide reductase
2. Vitamin K epoxide reductase activates Vitamin K which is a clotting factor
3. anti-coagulent
Reversible Enzyme inhibitors > Competitive > Statin
1. What do statins inhibit?
2. What is the enzyme involved in?
3. What agents are statins?
1. HMG CoA reductase
2. Cholesterol synthesis
3. Hyperlipidemic agents
Reversible Enzyme inhibitors > Competitive > Viagra (Sildenafil)
1.What enzyme does it inhibit and what does it compete with?
2. What is this enzyme involved in?
3. How does PDE5 work?
1. Inhibits cGMP Phosphodiesterase type V (PDE5) by mimicking cGMP
2. Nitric Oxide production for erection
3. PDE5 degrades cGMP = losing erection
-inhibitor delays cGMP break down = prolongs erection
Explain the Angiotensin system pathway
Liver makes Angiotensin > Angiotensin 1 >(Angiotensin Converting Enzyme)> Angiotensin 2 > Angiotensin 2 raises blood pressure
Reversible Enzyme inhibitors > Competitive > ACE Inhibitors (Captopril and Enalopril)
1.What enzyme does it inhibit?
2.What is this enzyme involved in?
3.What does the inhibitor help do?
1. Inhibits Angiotensin Converting Enzyme
2.Involved in increasing blood pressure
3. Lower blood pressure
Reversible Enzyme inhibitors > Competitive > Ibuprofen/Acetaminophen
1. what enzyme does it inhibit? What does it compete with?
2. Are there any structural similarities between these inhibitors and arachidonic acid? why?
1. Cyclooxygenase, arachidonic acid
2.No, because they block the channel into enzyme active site not the actual enzyme site
Memorize enzyme inhibitors
Enzyme Diagnosis
1. What happens when tissues are damaged?
2. what do the levels of enzyme in blood tell you?
3.For enzymes that are tissue specific...
4. Pattern of enzyme release indicate
5. isoenzymes or izosymes are..
6. Upon recovery what happens to serum enzyme levels?
7. Ex: Myocardial Infraction
1. Enzymes leak out
2. Severity of tissue damage
3. Indicates damage to that specific tissue if observed in the blood
4. tissue or organ of origin
5. enzymes in different physiochemical forms that can be tissue specific
6. They return to normal
7. A spike in a specific heart type creatine kinase is observed, but first protein released is myoglobin.. troponins I and T are most commonly used in diagnosis
Memorize Enzyme Diagnosis
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