enzymes 2 Flashcards Preview

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Flashcards in enzymes 2 Deck (24):
1

what is vmax?

enzyme rate when the substrate is saturated

2

what is Km?

concentration at which v = 1/2 Vmax

3

hexokinase vs. glucokinase

hexokinase in peripheral tissues, lower Km
glucokinase in liver, higher km
catalyze same rxn

4

consequence of low vs high km

low km = more activity at lower substrate concentrations
high km= need high substrate concentration for enzyme activity

5

metabolism of ethanol

ethanol to acetaldehyde by alcohol dehydrogenase
acetaldehyde to acetate by acetaldehyde dehydrogenase

6

effects of acetaldehyde

toxic, very reactive

7

consequence of absence of low Km form of acetaldehyde dehydrogenase

mitochondrial form is low Km form, but if this is absent, much use cytosolic form which has high km- this means that there must be a higher substrate concentration for the high Km form to be active and higher concentration of acetaldehyde = more toxic effects, tachycardia and flushing

8

effect of competitive inhibitors on km? vmax?

km will increase
vmax unchanged

9

effect of noncompetitive inhibitors on km? vmax?

km unchanged
vmax will decrease - inhibitor stops the enzyme from working properly

10

effect of organophosphates on AchE active site

organophosphate will form a covalent bond with serine in the active site and prevent AchE from working properly

11

shape of substrate vs. velocity curve for allosteric enzymes

sigmoidal

12

effect of an activator on the curve

shift to left, increased activate at lower [S] = lower km

13

effect of inhibitor on the curve

shifts to right, decreased activity at lower [S] = higher km

14

R state vs t state

R state= low km, high activity
T state = high km, low activity

15

enzyme that regulates pyrimidine synthesis in e. coli

aspartate transcarboxylase

16

activator and inhibitor of aspartate transcarboxylase

activator = ATP
inhibitor = CTP
either can bbd to regulatory site

17

structure of aspartate transcarboxylase

6 catalytic subunits
6 regulatory subunits

18

which aa can be phosphorylated? (3)

serine
threonine
tyrosine

19

what is the effect of phosphorylation?

gives (-) charge, allows for the formation of more H bonds

20

describe regulation of protein kinase A

cAMP bind to the regulatory subunits, causing them to dissociate from the catalytic subunits, catalytic subunits free to bind substrate

21

what is the regulatory subunit of PKA an example of?

"pseudo-substrate"

22

effects of epinephrine on blood sugar

epinephrine increases blood sugar through a cAMP dependent mechanism- PKA will phosphorylate and activate phosphorylase (breaks down glycogen into glucose) AND will phosphorylate and inactivate glycogen synthase (synthesizes glycogen) == increased blood glucose

23

how does calmodulin active enzymes?

calmodulin-activated kinases are auto inhibited with pseudo-substrate, once activated, calmodulin will bind the pseudo-substrate to release the auto inhibition and free the active site to function as kinase

24

example of calmodulin dependent kinase

MLCK