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47 Cards in this Set

  • Front
  • Back
Are most inhibitors covalent or noncovalent?
inhibitor is structurally similar to the transition state
competitive inhibitor
prevents the actual substrate from binding
competitive inhibitor

inhibitor binds either the enzyme or enzyme-substrate complex


What are the three common types of reversible inhibition?




What is an example of a neurotransmitter?

glutamic acid

What is NMDA?

When activated (NMDAR), it's a Ca+2 channel.
What does NMDA require to become activated NMDAR?
binding of glutamate and glycine

What kind of inhibitor is kynurenic acid on NMDAR?

competitive glycine antagonist

What happens to Km in a Michaelis-Menten plot as competitive inhibitor concentration increases?

larger apparent Km
What is [I] equal to on a Lineweaver-Burk Plot?
What happens to the slope of the Lineweaver-Burk Plot as competitive inhibitor concentration increases?

Does a better inhibitor have a higher or lower KI and why?

lower, binds tight to enzyme

What is KI?

inhibition constant
What equation features KI?
apparent Km = Km(1 + [I]/KI)

What is the effect of an uncompetitive inhibitor on Vmax?


What is the effect of an uncompetitive inhibitor on Km?


What does a low KI mean in terms of the equilibrium of bound and unbound?

inhibitors mostly bound

What kind of inhibitor is ethanol on NMDAR?

When does ethanol bind to Ca+2 channel of NMDAR?
in the presence of both ligands (E and G)
What does the double-reciprocal plot of uncompetitive inhibition look like?
parallel to no inhibitor

What kind of inhibitor is PCP on NMDAR?

noncompetitive antagonist

changes shape of receptor

noncompetitive inhibition
In what time frame does protein synthesis and degradation occur?

minutes to hours

In what time frame does compartmentalization occur?
minutes to hours

In what time frame does covalent modification called "interconvertible enzymes" occur?

seconds or less

In what time frame does non-covalent association called "allosteric enzymes" occur?

seconds or less
What typically require two "converter" enzymes? Explain.

interconvertible enzymes

One to turn on, one to turn off.

What do converter enzymes promote?

covalent modification

What amino acids can be phosphorylated?


What class of enzymes adds phosphates to a molecule?


True or false: kinases typically involve the active site.


What class of enzymes removes phosphates from a molecule?


What are allosteric enzymes modulated by?

activators or inhibitors that do not resemble the substrate S and bind at sites other than catalytic sites
often possess oligomeric structures (they possess quaternary structure)
allosteric enzymes
often display cooperativity
allosteric enzymes
What are the two typical forms of allosteric oligomeric enzymes?

active (R=relaxed)

inactive (T=tense)

stabilize active form (R state)


stabilize inactive form (T state)


True or false: an allosteric inhibitor decreases apparent Km.

false, activator
What does the curve of an enzyme plus an activator look like?
hyperbolic curve

What does an allosteric inhibitor do to the curve?

shifts it to the right as apparent Km increases

What is the concerted model of cooperativity?

binding of 1st substrate fully converts enzyme to R form

What is the sequential model of cooperativity?

substrate must be bound in all subunits before enzyme fully in R form
What model of cooperativity seems most likely experimentally?

What model of cooperativity seems most likely mathematically?

can't distinguish between them
Why does allosteric regulation of an enzyme occur?
Effector binding induces conformational changes in the enzyme.