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12 Cards in this Set
- Front
- Back
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Enzyme inhibitors: What are they? |
They are molecular agents that interfere with catalysis, slowing or halting enzymatic reactions. |
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Reversible inhibitors: What are they? What types are there? |
Compounds that bind and dissociate to the enzyme. There are two types: competitive and uncompetitive. |
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Competitive inhibitors: What is their function? How are they counteracted? How is their M-M graph? How is their L-B plot? |
They compete with the substrate for active of the enzyme to prevent it from binding with the substrate. Many of them are compounds that resemble the substrate. By adding more substrate, inhibitor molecules will more likely bind to the substrate than the enzyme. Their graph is slightly below the normal (uninhibited) one (since more substrate is needed to obtain same Vmax) with the same Vmax. However, Km is higher (but is only apparent). Their L-B plot is more vertical than the normal one. Km is higher so it is less negative, but Vmax is the same. |
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Uncompetitive inhibitors: What is their function? How is their M-M graph? Howis their L-B plot? |
They bind at a site different from active site and bind only to the ES complex (instead of just the enzyme). Their M-M graph will be below the normal one with a lower Vmax and lower apparent Km, but with no change in slope. Since active sites are available, less substrate is needed to saturate enzymes compared to with competitive inhibitors. In their L-B plot, the graph is parallel and above the normal one with a more negative 1/Km and a higher 1/Vmax. |
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Mixed inhibitors: What is their function? How is their L-B plot? |
They bind at a site district from active site of enzyme, but it binds to either E or ES complex. Their L-B plot is more vertical than the normal one, intersecting in the upper left quadrant with a higher 1/Vmax (therefore smaller Vmax) but less negative Km. |
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Noncompetitive inhibitors: What is their function? |
They bind to non-active site to induce a conformational change. In their M-M graph, their line is much lower than normal with a lower Vmax, but same Km since enzyme’s affinity has not changed. In their L-B plot, their graph is slightly more vertical with the same 1/Km, but higher 1/Vmax. |
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Regulatory enzymes: What are they? How are they affected by certain signals? |
Enzymes that have a greater effect on the rate of the overall sequence. They exhibit increased or decreased catalytic activity in response to certain signals. |
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Allosteric enzymes: What are they? How are they different from typical enzymes? How do they react to modulator binding? What is homoallostery? What is heteroallostery? |
They are a class of enzymes that reversibly bind (through noncovalent interactions) to allosteric modulators (effectors). They have an additional regulatory site for modulators to bind to. They undergo conformation changes in response to modulator binding into either the more-active or less-active form of itself. Homoallostery is the substrate induced regulation of allosteric enzymes (aka substrate and modulator are the same), so active site and regulatory site are the same. Heteroallostery is regulation of allosteric enzymes by a molecule other than the substrate. |
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Covalent modification: What is it? |
It is the reversible linking and removing of groups (by a separate enzyme) from a class of regulatory enzymes that will either activate the deactivate the enzyme. The most common covalent modification is phosphorylation. |
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Feedback inhibition: What is it? |
It is when the regulatory enzyme is inhibited by the end product of the pathway when [C] of it exceeds the cell’s requirements, slowing down the rest of the process. |
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Protein kinases vs. protein phosphatases: What is the difference b/w the two? |
Protein kinases catalyze attachment of phosphoryl groups to amino acid residues of a protein whereas protein phosphatase catalyze the removal of phosphoric groups. |
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Irreversible Regulation: What are the two types? |
They include proteolytic cleavage of peptide segments (processing) and covalent bonding. |
