L23- Regulation of protein function

Question 1

the regulation of enzyme activity can be

Answer 1

short term or long term

Question 2

short term regulation of enzyme activity

Answer 2

1. Substrate and product concentration

2. Change in enzyme conformation

Question 3

change in enzyme conformation

Answer 3

• Allosteric regulation
• Covalent modification
• Proteolytic cleavage

Question 4

long term regulation

Answer 4

1. Change in rate of protein synthesis

2. Change in rate of protein degradation

Question 5

substrate availability will affect

Answer 5

the rate of enzyme activity

Question 6

isoenzymes

Answer 6

different forms of the same enzyme that have different kinetic properties

Question 7

example of isoenzymes

Answer 7

heoxkinase and glucoses kinase (lower affinity)

Question 8

as the concentration of product increases

Answer 8

the rate of enzyme activity should increase

Question 9

hexokinase shows

Answer 9

hyperbolic activity

Question 10

product inhibition

Answer 10

Accumulation of the product of a reaction inhibits the forward reaction e.g. glucose-6 phosphate inhibits hexokinase activity

Question 11

change in rate of protein synthesis

Answer 11

enzyme induction/ repression

Question 12

change in rate of protein degradation

Answer 12

ubiquitin-proteasome pathway

Question 13

allosteric enzymes show

Answer 13

a sigmoidal relationship between rate and substrate concentration- instead of the rectangular hyperbola seen for the simple enzyme

e.g. BPG and Hb

Question 14

allosteric activators

Answer 14

increase the proportion of enzyme in the R state 9high affinity)

Question 15

Allosteric inhibitors

Answer 15

increase the proportion of enzyme in the T state

Question 16

Substrate binding to one subunit makes

Answer 16

subsequent binding to other subunits progressively easier

o E.g. Hb

Question 17

allostatic regulation of phosphofructokinase (sets pace for glycolysis): activators

Answer 17

low energy signal

• AMP
• fructose 2-6, bisphopshate

Question 18

allostatic regulation of phosphofructokinase (sets pace for glycolysis): inhibitors

Answer 18

high energy signals
o ATP
o Citrate
o H+

Question 19

protein kinases

Answer 19

transfer the terminal phosphate from ATP to the OH groups of Der, The, Tyr

Question 20

phsophorylation

Answer 20

activation of a protein

Question 21

why is protein phosphorylation so effective

Answer 21

• Adds 2 negative charges

- A phosphoryl group can make H-bonds

Question 22

protein phosphatases

Answer 22

reverse the effect of kinases by catalysing the hydrolytic removal of phosphoryl groups from proteins

Question 23

when enzymes activate enzymes…

Answer 23

the number of affected molecules increase geometrically in an enzyme cascade

Question 24

amplification of signals by kinase cascades allows

Answer 24

amplification of the initial signal by several orders of magnitude within a few milliseconds

Question 25

many enzymes are activated by

Answer 25

specific proteolytic cleavage

Question 26

symogens

Answer 26

inactive precurosers

• specific proteolysis is a common means of activating enzymes in biological ssytems

Question 27

zymogen of pepsin

Answer 27

pepsinogen

- released into the stomach from the pancreas

Question 28

zymogen of trypsin

Answer 28

trypsinogen

Question 29

often activation of zymogen involves

Answer 29

proteolysis of T and C terminals