Term
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Definition
1) Specialized protein that catalyze substrate to a product
2) Does so by lowering activation energy under physiological conditions (temperature, pH, and pressure), does NOT alter equilibrium of rxn.
3) Activation energy is lowered during the transition state through multiple WEAK interactions. |
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Term
| Basic Things About Enzymes |
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Definition
| 1) Activation site is designed to be very efficient at catalysis (lower activation energy) and a high degree of specificity. 2) Activation site provides an environmental that helps stabilizes unstable intermediate. 3) Enzymes are bigger than substrate, cofactors, and products. |
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Definition
| 1) Oxidoreductases 2) Transferases 3) Hydrolases 4) Lyases 5) Isomerases 6) Ligases |
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Term
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Definition
| 1) Some enzymes require cofactors that can be inorganic (generally smaller), complex organic or metalloogranic molecules called COENZYMES (generally larger). |
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Definition
1-2 for Pepsin
7.8 for glucose-6-phosphate
pH also impacts SUBSTRATE |
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Term
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Definition
| Above 40C, many enzymes denature and lose their functionality. |
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Term
| Measurement of enzyme activity (units) |
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Definition
[E]+[S]-->[ES]-->[EP]-->[E]+[P]
Measure loss of S or formation of P.
1)Unit of Activity = umol P formed/sec
2)SPECIFIC activity = umol P formed/sec/mg of protein OR unity of activity/mg. ASSESSES PURITY of enzyme. |
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Term
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Definition
Separate enzymes that perform the same function often coded by different genes & different isozymes are expressed in different tissues.
LDH (lactate dehydrogenase) is a tetramer, coded by two genes (one for the H and the S subunit respectively). Five forms exist.
-LDH1-heart (positive charge)
-LDH5-liver (negative charge) |
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Term
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Definition
| Separates out proteins based on mass to charge ratio. |
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Term
| Activation Energy versus Free Energy |
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Definition
Enzymes do NOT change the free energy, just the activation energy and it is through WEAK interactions.
Activation Energy are barriers to chemical reactions, rate of change decreases as activation energy increases. |
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Term
| Examples of Enzyme Catalysis (4) |
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Definition
1) Substrate Strain
2) Proximity Effects
3) Functional groups in active site carry out general acid/base catalysis
4) Covalent Catalysis |
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Term
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Definition
1. What catalytic power of enzyme is derived from (formation of many weak bonds and interactions--hydrogen bonds, hydrophobic and ionic interactions). Contributes to SPECIFICITY as well as catalysis.
2. Weak interactions are optimized in the reaction TRANSITION STATE NOT the ACTIVE SITES. *IMPORTANT POINT* |
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Term
| Enzyme Induced Substrate Strain |
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Definition
Lysozyme cleaves glycans at beta(1 through 4) glycosidic links.
SPECIFICALLY positions substrate for catalysis. (Orientation+Specificity)
acetamido binds to active site.
lactyl side group has to face away from enzyme.
every other pyranose ring undergoes a change into a half-chair conformation. |
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Term
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Definition
Freedom of motion is greatest to least from (entropy decreases)
1) Bimolecular reaction
2) Reactive groups in one molecule (bonds can rotate)
3) Bonds can't rotate, "shackled to each other."
Substrate strain lowers free energy barrier by causing transition state to become favorable.
NADPH cofactor, dihydrofolate reductase substrate. |
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Term
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Definition
Hydrolyzes peptide bonds adjacent to large aromatic AAs like Trp, Try, and Phe.
Like Trypsin, it is a SERINE PROTEASE.
Ser 195 O-H
His 57 N-H
Three different regions in active site--active site, oxyanion hole (stabilize rxn), and aromatic pocket (oriented substrate in active site).
FORMS COVALENT BOND WITH ENZYME (forms acyl tetrahydral intermediates) |
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Term
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Definition
Ser and Cys Proteases involve covalent catalysis.
Aspartyl and Metalloproteases have no covalent catalysis; base catalysis (activated water). |
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Term
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Definition
Hydrophobic pocket-Chymotrypsin
Salt bridge-Trypsin
Small hydrophobic pocket-Elastase |
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Term
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Definition
| HIV Proteases cleaves peptide bonds between Phe and Pro. There is NON-COVALENT CATALYSIS. Two different Asp groups (O-H) act as acid-base catalyst, faciliating attack of water on peptide bond. |
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Term
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Definition
Always a hydroxyl group next to a benzyl group. The benzyl group positions the inhibitor and the hydroxyl acts as a transition state analog.
Form NON-COVALENT complexes with enzyme.
Considered irreversible inhibitors (technically, it's a tight-binding inhibitor).
Transition-site inhibitor. |
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Term
| Liver Alcohol Dehydrogenase (ALDH) |
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Definition
E487K mutation.
Glutamate-->Lysine (acid-->basic)
Only matters if mutation affects active site or one of the stabilizers of the tetrahedral intermediate. |
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