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14 Cards in this Set
- Front
- Back
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What are the ways to regulate enzyme activity?
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Isozymes, enzyme concentration, covalent modification, cooperativity/allosteric regulation, substrate/co-factor availability, inhibition
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What is the main example used for isozymes? How do alternative subunits lead to difference in electrophoresis? What is the biological role?
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Lactage dehydrogenase isozymes (5 of them, different kinds of H and M subunits mixed together in tetramer)
Slightly different charges, which is why they can be separated by electrophoresis Slightly different catalytic properties as well |
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In exercising, muscle uses up all O2, leading to eventual loss of NAD+, stopping glycolysis. How is this alleviated by LDH isozymes?
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LDH5 uses pyruvate to obtain more NAD+ (lactate is also formed) this is anaerobic respiration
Lactate eventually goes out to blood and into liver Liver gluconeogenesis (continues glycolysis) |
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Conversely to LDH5 and gluconeogenesis, what does LDH1 and the heart do?
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It's the opposite direction
Heart is O2 rich (doesnt need to wait on liver for glucose) prefers to pick up lactate straight from blood, make pyruvate and make glucose (reverse reaction) |
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Drugs can also target alternative isozymes. Talk about COX? What some examples of drugs? What is the difference between COx 1 and 2?
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Cyclooxygenase transforms arachidonic acid to prostaglandin H2 (inflammation and pain response)
By inhibiting COX, you block inflammation and pain Ex: ibuprofen and aspirin COX2 is the inflammatory cells (has valine) has a smaller AA and has bigger ligand binding site Cox1 has Ile and is constitutive |
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Enzyme concentration: When you change enzyme concentration, what do you change on the graph?
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You change Vmax
More enzyme=up Vmax Less enzyme=lower Vmax (decreased enzyme activity) |
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What happens to Km when you change enzyme concentration?
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NOTHING
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In ethanol metabolism, what are the two enzyme players? which is more predominant? What happens with Cyt isozymes with excessive drinking??
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alcohol dehydrogenase and cytochrome p450 (ADH and CytP450)
ADH does the majority of the metabolism of ethanol, but with excessive amounts, ADH gets overwhelmed and the body responds by upregulate CytP450 Isozyme CYP2E1 also gets increased (5 to 10x)--increases mRNA and decreases degradation ALL CytP isozymes are increased at once, and all drug metabolism is enhanced |
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What are the two main ways for covalent modification of enzymes? Which is reversible?
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Phosphorylation (reversible)
Proteolysis (not reversible) |
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Proteases are frequently controlled by what covalent modification? What is the cascade? What is active and inactive?
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Proteolysis
Preproenzyme (translated from mRNA, leader sequence for location, inactive) Proenzyme aka zymogen(IN THE RIGHT LOCATION) leader sequence CLEAVED, still inactive Mature protease: other region of the protease cleaved, ACTIVE form |
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Pancreatic Digestive Enzyme: What is the cascade to go from inactive (-gens) to active form in the pancrease? Why is this done?
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You dont want enzymes to chomp up substrates on its way out from pancreas to right location in small intestine
So, they travel in the -gen inactive form. Trypsinogen gets to small intestine, and enteropeptidase cleaves it and makes it into the active trypsin, which then goes and activates the other proteases so they are active Small intestine: enteropeptidase Others: made in pancreas chymotrypsin gets cleaved partially by trypsin and goes on and cleaves and activates other things (3 peptide chains in the most active form) |
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What is caspase?
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Protease involved with apoptosis
Turned on for apoptosis when needed (eats cell from inside out) 1polypeptide with a prodomain, at least 2 cleavage steps before it does its magic |
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Enzymes also have cooperativity and allostery. In a plot with x=[substrate], enzymes appear hyperbolic or slightly sigmoidal. Enzymes are more complicated than ligand binding because: 1. affect how the substrate binds to enzyme or 2. they can change the catalytic properties of the reaction. Therefore, they can change.....
And where do they change on the graph? |
Kcat and/or Km
Km is left or right (affects rate of catalysis) Kcat in the michaelis menten equation: Vmax and Km::Kcat is part of Vmax If you alter Kcat, you alter Vmax Altered Kcat (Vmax is lowered or highered) |
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What does cooperativity /allostery tell you about the protein structure of the enzyme?
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Cooperativity multiple same binding sites
Allostery multiple different same binding sites |
