Lecture 11 Mechanisms Of Enzymes

Front 1

Are most inhibitors covalent or noncovalent?

Back 1

noncovalent

Front 2

inhibitor is structurally similar to the transition state

Back 2

competitive inhibitor

Front 3

prevents the actual substrate from binding

Back 3

competitive inhibitor

Front 4

inhibitor binds either the enzyme or enzyme-substrate complex

Back 4

noncompetitive

Front 5

What are the three common types of reversible inhibition?

Back 5

competitive

uncompetitive

noncompetitive

Front 6

What is an example of a neurotransmitter?

Back 6

glutamic acid

Front 7

What is NMDA?

Back 7

When activated (NMDAR), it's a Ca+2 channel.

Front 8

What does NMDA require to become activated NMDAR?

Back 8

binding of glutamate and glycine

Front 9

What kind of inhibitor is kynurenic acid on NMDAR?

Back 9

competitive glycine antagonist

Front 10

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

Back 10

larger apparent Km

Front 11

What is [I] equal to on a Lineweaver-Burk Plot?

Back 11

slope

Front 12

What happens to the slope of the Lineweaver-Burk Plot as competitive inhibitor concentration increases?

Back 12

steepens

Front 13

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

Back 13

lower, binds tight to enzyme

Front 14

What is KI?

Back 14

inhibition constant

Front 15

What equation features KI?

Back 15

apparent Km = Km(1 + [I]/KI)

Front 16

What is the effect of an uncompetitive inhibitor on Vmax?

Back 16

lowers

Front 17

What is the effect of an uncompetitive inhibitor on Km?

Back 17

lowers

Front 18

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

Back 18

inhibitors mostly bound

Front 19

What kind of inhibitor is ethanol on NMDAR?

Back 19

uncompetitive

Front 20

When does ethanol bind to Ca+2 channel of NMDAR?

Back 20

in the presence of both ligands (E and G)

Front 21

What does the double-reciprocal plot of uncompetitive inhibition look like?

Back 21

parallel to no inhibitor

Front 22

What kind of inhibitor is PCP on NMDAR?

Back 22

noncompetitive antagonist

Front 23

changes shape of receptor

Back 23

noncompetitive inhibition

Front 24

In what time frame does protein synthesis and degradation occur?

Back 24

minutes to hours

Front 25

In what time frame does compartmentalization occur?

Back 25

minutes to hours

Front 26

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

Back 26

seconds or less

Front 27

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

Back 27

seconds or less

Front 28

What typically require two "converter" enzymes? Explain.

Back 28

interconvertible enzymes

One to turn on, one to turn off.

Front 29

What do converter enzymes promote?

Back 29

covalent modification

Front 30

What amino acids can be phosphorylated?

Back 30

STYH

Front 31

What class of enzymes adds phosphates to a molecule?

Back 31

kinases

Front 32

True or false: kinases typically involve the active site.

Back 32

false

Front 33

What class of enzymes removes phosphates from a molecule?

Back 33

phosphatases

Front 34

What are allosteric enzymes modulated by?

Back 34

activators or inhibitors that do not resemble the substrate S and bind at sites other than catalytic sites

Front 35

often possess oligomeric structures (they possess quaternary structure)

Back 35

allosteric enzymes

Front 36

often display cooperativity

Back 36

allosteric enzymes

Front 37

What are the two typical forms of allosteric oligomeric enzymes?

Back 37

active (R=relaxed)

inactive (T=tense)

Front 38

stabilize active form (R state)

Back 38

activators

Front 39

stabilize inactive form (T state)

Back 39

inhibitors

Front 40

True or false: an allosteric inhibitor decreases apparent Km.

Back 40

false, activator

Front 41

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

Back 41

hyperbolic curve

Front 42

What does an allosteric inhibitor do to the curve?

Back 42

shifts it to the right as apparent Km increases

Front 43

What is the concerted model of cooperativity?

Back 43

binding of 1st substrate fully converts enzyme to R form

Front 44

What is the sequential model of cooperativity?

Back 44

substrate must be bound in all subunits before enzyme fully in R form

Front 45

What model of cooperativity seems most likely experimentally?

Back 45

concerted

Front 46

What model of cooperativity seems most likely mathematically?

Back 46

can't distinguish between them

Front 47

Why does allosteric regulation of an enzyme occur?

Back 47

Effector binding induces conformational changes in the enzyme.