Lecture 14, Regulation (Ford) Flashcards
How are metabolic enzymes regulated?
Compartmentalization, enzyme concentration, enzyme activity, hormone signals
How can reactions be affected?
Substrate-level control or feedback control
What kind of reaction does substrate-level control act on?
Single reaction
What kind of reaction does feedback control act on?
Targets a different step in the pathway
How is product formation affected by feedback?
Activators promote more product; inhibitors prevent more products
What are isozymes?
Catalyze the same reaction but with different efficiencies
T or F: Isozymes are compartmentalized based on tissue specificity.
True.
During development, what kind of expression do isozymes utilize?
Temporal
What can be added via reversible covalent modification?
Functional groups
How would the addition of functional groups affect an enzyme?
Activate or deactivate the enzyme
What are some common functional group additions?
Myristic acid, farnesyl, nucleic acids, ubiquitin, carbohydrates, small molecules
What is the greatest source of diversity to the proteome?
Addition of carbohydrates
What are the sources of diversity when carbohydrates are added via covalent modifications?
O- vs. N- linkages, composition of sugars, branched vs. unbranched, length of oligosaccharide
What are some common small molecule additions?
Gamma-carboxylation, sulfation, acetylation, methylation, phosphorylation
T or F: Acetylation tends to be deactivating.
False. Acetylation tends to be activating.
What types of covalent modification can histones experience?
Acetylate, methylate, phosphorylate
Why is phosphorylation activating regarding thermodynamics?
ATP hydrolysis can drive unfavorable reactions (-deltaG)
Why is phosphorylation activating regarding kinetics?
Physiological processes dictate reaction rate
Why is phosphorylation activating regarding cell processes?
ATP amounts dictated by metabolism (energy charge); Signal transduction amplification (catalytic turnover)
Why is phosphorylation activating regarding shape and charge complementarity?
Each phosphate adds -2 charge and 3+ H bonds
T or F: Phosphatases remove phosphates, while kinases add phosphates.
True.
What does the name of a kinase indicate?
On which amino acid the phosphate will be added
T or F: A tyrosine kinase will add a phosphate to a serine.
False. A tyrosine kinase will add a phosphate to a tyrosine.
Where is covalent modification happening?
Allosteric site
What is heteroallostery?
Effector binds at allosteric site
What is homoallostery?
Cooperativity
What is ATCase inhibited by?
CTP
The binding of CTP prefers which state?
T (inactive) state
The binding of ATP prefers which state?
R (active) state
How is it determined when covalent modification happens?
Enzyme amount (protein synthesis regulation = on/off switch)
What are the 2 levels of control that are possible during protein synthesis regulation?
Transcription regulation at the promoters; Translation regulation at the UTRs
Histone phosphorylation ___ transcription.
Prevents
Histone methylation can ___ or ___ transcription.
Prevent or promote
T or F: mRNA levels correlate to protein levels.
False. mRNA levels do not correlate to protein levels.
Why are enzymes regulated?
Irreversible covalent modifications (proteolytic activation)
What is the inactive form of an enzyme called?
Zymogens (take something away) or apoenzymes (add something)
What are some examples of enzymes that begin their lives as zymogens?
Proteases, collagen, blood clotting factors, insulin/hormones
Chymotrypsin is an example of what kind of protease?
Serine protease
How many times must chymotrypsin be cleaved to be activated?
Twice
What type of reaction makes a disulfide bond?
Oxidation
What amino acid must be present in order to have a disulfide bond?
Cysteine
