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17 Cards in this Set

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  • Back
What is allostery in enzymes?
Activity of enzyme modulated by positive or negative allosteric effectors.
What are isozymes?
Distinct polypeptides that catalyze the same reaction to fine tune metabolism (e.g.: muscle isozyme works for anerobic and high Km, heart isozyme works for aerobic at low Km)??
What are three ways to activate enzyme activity?
1) Phosphorylation (eg: Pyrvuate kinase)
2) Proteolytic (eg: zymogen activation by trypsin and blood coagulation cascade)
3) Cooperativity and alloery (hemoglobin)
What happens if there is a pyruvate kinase deficiency?
Anemia - Atp required for biconcave shape, deficiency causes reduction in glycolysis and lowered ATP levels, which causes cells to be lost rapidly with anemia since precursor cells cnanot compensate sufficiently
What important zymogens does trypsin activate?
Proelastase to Elastase and chymotrypsinogen to chymotrypsin.
What is the significance of the step between thrombin and fibrin in the blood coagulation cascade for blood clot formation?
Thrombin will cleave at alpha and beta chain to remove tails, which allows fibrin to undergo polymerization to form a clot.
What is the difference between homotropic and heterotropic effectors?
Homotropic is where the molecule that induces the effect is similar to the substrate

Heterotropic is when the molecule that induces the effect is different from substrate.
What are the two models of homotropic effectors?
1) Concerted - dimeric enzyme, binding of first substrate has effect on binding of second substrate
2) Sequential -four subunits, binding of 1st substrate facilitates binding of following substrates
What are the inactive and active states called?
T and R
For a protein to exhibit cooperativity, what must its Hill plot slope be? for non-cooperativity
greater than 1 to be cooperative

Describe monomeric heterotropic effects.
3 binding sites - substrate, activator and inhibitor. Activator or inhibitor can bind, and then substrate either can bind or cannot bind to the one subunit (monomeric).
What is heterotropic allostery?
Involves molecules other than substrate in pathway.
What are the two types of heterotropic allostery?
Monomeric and oligomeric.
Will increase in BPG (2,3-Biphosphoglycerate) increase or decrease the O2 affinity of hemoglobin, and how is this advantageous at high altitudes?
It will lower the affinity of hemoglobin for oxygen. This will allow more oxygen to be delivered to the tissues at high altitudes.
What is the difference b/n non-competitive inhibition and allostery?
You don't change the Km value in non-competitive inhibition, whereas in allostery you prevent substrate from binding in the first place.
Protein-protein interactions have what consequence for regulation, specifically with Protein Kinase A and cAMP?
keep enzyme in inactive state until activated
What is the mechanism of ubiquitinization for degradation of proteins in proteasomes to smaller peptides?
Ubiquitin added to lysine sidechain via isopeptide bond. Involves three distinct enzymes in a multi-step process.