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bich test 3
| Question | Answer |
|---|---|
| oxidoreductase | catalyze oxidation/reduction reactions NAD/NADH |
| transferase | catalyze group transfer |
| hydrolase | catalize hydrolysis reactions look for water! |
| lyase | catalize lysis of substrate generate a double bond often called "synthases" |
| isomerase | structural change within a SINGLE monecule |
| ligase | catalize a joining of two molectules (ligation) require energy input often called "synthETases" |
| cofactor | a small metal ion that is associated with an enzyme that facilitates the reaction |
| coenzyme | a small organic molecule that is associated with an enzyme that facilitates the reaction |
| cosubstrate | a coenzyme or cofactor that only has transient/loose association with the enzyme another enzyme regenerates the coenzyme/cofactor |
| Prosthetic group | coenzyme that has Permanent association with the enzyme a separate phase of the same enzymatic reaction sequence allows for the coenzyme/cofactor to regenerate |
| Arrhenius equation | e^(-dG**/RT) |
| rate enhancement equation | e^(ddG**/RT) Kcatalyzed/Kuncatalyzed |
| three assumptions for MM equation | 1. don't have a high [] of enzyme in bio. systems, so [S]t=[S]free 2. ignore the backwards-catalyzed rxn 3. upon mixing E+S, [ES] reaches a STEADY STATE EQ. Vmax=K2[ES] |
| MM equation | Vo=(Vmax[S]t)/(Km+[S]t) |
| catalytic constant (turnover number) | Kcat=Vmax/[E]t |
| catalytic efficiency | =-Kcat/Km |
| reversible inhibitor | a substance that binds to an enzyme to inhibit it, but can be released non-covalent bonds Dead End or Product |
| Dead End reversible inhibitor | a compound that is NOT part of the rxn, but looks like either a substrate or a product |
| Product reversible inhibitor | the product of a reaction inhibits the enzyme that catalyzes the enzyme is part of a normal reaction |
| irreversible inhibitor | a substance the causes inhibition that cannot be reversed covalent bonds preferred in drugs over reversible inhibitor |
| competitive inhobitor | competes with the substrate for the enzyme-substrate binding site double reciprocal plot: lines cross on y-axis R=Km(I)/Km(noI)=slope(I)/slope(noI) |
| uncompetitive inhibitor | binds to enzyme substrate complex parallel lines on double reciprocal plot R=yint(I)/yint(noI)=xint(I)/xint(noI) |
| mixed inhibitor | bind to E and ES in unequal amounts if KiKi' lines cross in 3rd R=yint(I)/yint(noI)=slope(I)/slope(noI) |
| pure non-competitive | binds to E and ES in equal amounts (Ki=Ki') lines cross on x axis on double reciprocal plot R=yint(I)/yint(noI)=slope(I)/slope(noI) |
| Equilibrium constant of inhibitor (Ki) | Ki=[I]/(R-1) |
| sequential raction | all substrates must bind to the enzyme before the reaction occurs and products are released will have intersecting lines on Vo double reciprocal plot |
| ordered sequantial rxn | substrates bind in a specific order and products come off in a specific order (A on, B on, rxn, P off, Q off) |
| random sequantial rxn | all products come on before rxn occurs, but in any order (A or B on, A or B on, rxn, P or Q off, P or Q off) |
| ping-pong rxn | one or more products are released before all substrates have been added; alternate stable enzyme form (F) is produced in the half reaction will have parallel lines on Vo double reciprocal plot |
| proximity and orientation effect | substrates are oriented in the optimum way for chemistry to occur reduces entropy |
| transition state optimization | complimentarity to substrate less helpful than complimentarity to transition state; need a space for rxn. to occur |
| three basic types of enzyme mechanisms | acid-base catalysis covalent catalysis metal ion catalysis |
| types of acid-base catalysis | general acid catalysis general base catalysis concerted acid-base catalysis |
| general acid catalysis | general acid DONATES a PROTON to substrate enzyme active site must be protonated |
| general base catalysis | general base ACCEPTS a PROTON from the substrate enzyme active site must be deprotonated |
| concerted acid-base catalysis | a general acid and a general base (on enzyme) both participate in the reaction with the substrate |
| covalent catalysis | covalent bond is transiently formed between the substrate and the enzyme (or coenzyme) usually a NUCLEOPHILIC group on ENZYME and [electrophilic] group on [substrate] |
| metalloenzymes | enzymes that contain tightly bound metal cofactors |
| metal activated enzymes | enzymes that are only loosely bound to metal ions |
| Serine protease examples | -thrombin (blood clotting) -(chymo)trypsin, elastase (digestive enzyme) -subtilisin (bacterial protease) -plasmin (anti-clot) -tissue plasminogen activator (TPA, makes plasmin, stroke indicator) |
| the catalytic triad | the active sites of trypsin, chymotrypsin, and elastase are all composed of His, Asp, and Ser |
| zymogens (proenzymes) | inactive precursors that are irreversibly activated by specific proteolytic cleavage |
| isozymes | enzymes with similar but not identical aa sequence and catalyze the SAME rxn different Km and Vmax values use different effectors/forms of enzyme e.g. lactate dehydrogenase (A4 is glucokinase, liver; is hexokinase in muscles) |
| allosteric regulation | used for multi-subunit proteins, do NOT obey M-M kinetics (sigmoidal instead of hyperbolic) |
| covalent modification | enzymes are used to convert the regulatory enzyme to an active A form or inactive B form; reversible, covalent changes are made to specific aa side chains |
Created by:
jesters
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