Regulatory Strategies- Enzymes Flashcards
Define the concept of cooperation that may regulate enzyme activity.
Multiple subunits work together to bind a substrate.
Allosteric enzyme involve a regulatory chain TF
True (3 regulatory dimer, 2 regulatory trimer)
Describe what are homotrophic and heterotrophic effect in the context of enzymatic activity?
Heterotrophic effector = non-substrate molecules.
Homotrophic = shift the Km of the enzymes.
List the different regulatory mechanisms that control enzymatic activities.
Allostery - most common.
Covalent modification - phophorylation
Regulatory subunits
Isozymes and expression
Zymogen activation
Standard inhibition
All carbonic anhydrases catalyze the same reaction using the same mechanism TF
False?
What is the allosteric control of an enzyme?
Feedback inhibition
Enzyme is regulated by a distant product in the reaction.
Non-michaelis-menten kinetics.
Cooperativity.
Quaternary structure, because of multiple subunits. Multiple active sites give it a sigmoid graph.
Shows inhibition and activation.
Provide an example of proteolytic enzyme’s inhibitor? Describe how inhibition occurs from a molecular point.
Chymotrypsinogen. Forms Chymotrypsin protease that gets degraded, digestion, cleaves protein that is ingested. Inactive form is cleaved by trypsin to active. When Active it cleaves itself and the protein ingested. Cleavage changes conformation. Activation cascade, once cleaved, active forever. Inhibition stops activity.
Coagulation cascade. At the end of the cascade, short fibers are induced to stop bleeding.
Aspartate transcarbamoylase (ATCase) is regulated by regulatory subunit regulation TF
True
What classifies an enzyme as a protease?
Cleaves peptide bond
Does proteolysis need ATP? Why?
Yes. For the covalent conjugation to protein substates and stimulate activity of protease in order to degrade proteins
What are the characteristics of seine protease family member?
Homologous tertiary structure.
Trypsin and chymotrypsin have similar substrates
Resolves active site of enzymes
Same catalytic mechanism. Nucleophilic attack, acetylation, deacetylation
Carbonic anhydrases are not all homologous to each other. TF
False. Three families due to convergent evolution.
What are isoenzymes and isozymes? How they differ? Do the?
Isozymes: replaced by similar enzymes, but do not have the same function as the original.
Isoenzymes: enzymes that differ in amino acid sequence but catalyse the same reaction
Describe the regulatory and catalytic subunit interaction of protein kinase A PKA
Regulatory subunit induces phosphorylation. Not catalyzed by a committed step.
CAMP binding domains, cAmp is the regulatory subunit. Binding induces conformation change and can activate.
How is it possible to amplify catalytic activity(similarly to signal amplificaiton? Example?
Catalytic power of enzymes; enzymes catalyze the production of signaling molecules and then the signal received at cell surface is amplified.
- Glutamine synthetase shows the most perfectly simple saturating curve in Michaelis-Menten analysis. True or False
False? It is non-michaelis-menten)
Allosteric enzymes have sigmoidal Michaelis-Menten curves. True or False
False, non-Michaelis-menten
Some of Carbonic anhydrases are evolutionarily related to others of them. True or False
False, they are convergent evolution.
How is the antitrypsin inhibitor operating?
Inhibits elastase (a substance that breaks down tissue in the liver) operating as a protease inhibitor
Aspartate transcarbamoylase (ATCase) shows normal Michaelis-Menten kinetics. True or False
False, Allosteric control
How proteolytic cleavages occur?
By activating the enzyme and then breaking peptide bonds between amino acids
Carbonic anhydrases all chelate zinc ions. True or False
False
Glutamine synthetase has a quaternary structure made of twelve copies of the same subunit. True or False
it does have quaternary structure, need to find the twelve copies part.)
Allosteric enzymes catalyze the committed step reaction in a pathway. True or Fals
true
Allosteric enzymes are functional as a complex of more than one tertiary structure. True or False
True
Allosteric enzymes lack quaternary structure. True or False
False
Aspartate transcarbamoylase (ATCase) regulates the entire pathway of pyrimidine
nucleotide Allosteric enzymes have regulatory sites that do not overlap the active site. True or False
True
Glutamine synthetase is exquisitely regulated by more than a score of different compounds. True or False
T
Attaching a phosphate to a serine, threonine, or tyrosine residue on an enzyme will?
Begin reversible phosphorylation, regulating the activity of proteins, increasing communication and signals in cells, activate protein/enzyme, and adjust kinetic to physiological needs
When is the enzyme protein kinase A activated?
When it is phosphorylated
An enzyme that is synthesized as a zymogen is activated when?
Proteolytic cleavage happens OR when it cleaves itself
ATCase and Glutamine have ______ in common
Non-michealis-menten kinetics
Feedback-inhibited by pathway end-products
Qauternary structure
Up-regulated by some compounds.
There are other means of enzyme regulation in addition to standard inhibition, the most important biologically being allostery. What are the others?
Covalent modification
Regulatory subunits
Zymogen activation
Isozymes & Expression
