BC12 Enzyme Regulation

Question 1

Enzyme significance

Answer 1

control mechanism
avoid waste
conserve energy
adapt
coordinate
homeostasis

Question 2

Regulatory Enzyme characteristics

Answer 2

Rate limiting step
catalyzing step
Energy consumption step

Question 3

Non Covalent Interactions

Answer 3

spatial temporal separation (lysosomes)(pathway)
-rate limiting steps either direction
substrate availability  
-Vmax (cant go past)
product inhibition
allosteric regulation
protein protein interactions

Question 4

substrate availability

Answer 4

hexokinase and glucokinase both convert
glucose to glucose 6 phosphate

GK in liver: between 5 and 10 activity doubled
HX: would not change

Question 5

product inhibition

Answer 5

STRUCTURAL similarity to bind to active site
either immediate product or downstream product

Not like competitive inhibition because with increasing substrate comes increasing product so it will not dilute the inhibitor

NOT feedback inhibition-allosteric

Question 6

allosteric regulation

Answer 6

requires multiple subunits

modulators or effectors bind to CHANGE substrate CONFIRMATION

bind on REGULATORY site NOT active site.

Two subunits, one regulatory, one catalytic.

sigmoidal curves of reaction V vs substrate

presence of effector can alter the affinity for the substrate (K0.5)

homotropic/heterotropic
activator/inhibitor

Question 7

Feedback v Feedforward Regulation

Answer 7

ALLOSTERIC: downstream product inhibits or activates earlier in pathway

(whats the difference to product inhibition? DIFFERENT SITE ON MOLECULE

Question 8

ATCase

Answer 8

bacterial pyrimidine biosynthesis

ATCase: 6 cat 6 reg subunits

ATP/CTP are effectors

CTP end product and negative effector, binding to ATCase stabilizes AT form (tense) (higher Km, decreased affinity)

ATP is substrate and FEED FORWARD?? yes, more gives rise to more

Question 9

types of allosteric regulation

Answer 9

cooperativity: concerted, or sequential (Hb)
Inhibition
Activation
Modulation
Fusion, fusion of an enzyme to a protein

Question 10

protein protein interactions

Answer 10

binding of additional protein causes conformational change.

Glycogen phosphporylase by Calmodulin

GP breaks down glycogen

Ca2+ floods into cytoplasm, calmodulin binds (4-2on each end), calmodulin changes conformation to HUG, two hands wrap around biding site on target protein (activates it- stimulating glycogen synthesis)

white blood cells: elastase to destroy bac cell wells, but too much destroys tissue

alpha antiprotienase breacs it down. (binds to it and forms a complex inhibiting it)

smokers have oxidants that oxidize methionine residue blocking t from being able to bind

Question 11

covalent modification

Answer 11

phosphorylation   adds phosphate
adenylation   adds adenosine
Uridylylation adds uridine
adp ribosylationL adds ribose?
methylation adds methyl group

immediate effect on enzyme.

Question 12

proenzyme

Answer 12

inactive precursor to enzyme, also called zymogen

must be selectively cleaved to activate

Question 13

isoenzyme

Answer 13

different sequence, same reaction

Question 14

apoenzyme

Answer 14

enzyme without cofactor to be active, becomes haloenzyme