Enzyme - Factors Affecting Activity

Question 1

What can enzyme activity be affected by in vitro?

Answer 1

Inhibitors
Physical Factors
Cellular Regulation
Temperature

Question 2

What may temperature increase lea dto?

Answer 2

Thermal denaturation of weak bonds stabilising protein conformation with protein optimum

Question 3

How does pH affect enzyme activity?

Answer 3

Electrostatic interactions of enzyme and substrate by ionisation

Question 4

What is the average enzyme optimum?

Answer 4

5-8

Question 5

What are the pH optimum of digestive and intestinal enzymes?

Answer 5

2 and 8

Question 6

What concentrations regulate enzyme activity?

Answer 6

Substrate and Product

Question 7

When might product inhibition occur?

Answer 7

The more the substrate hte more the product

Question 8

What does product inhibition affect?

Answer 8

Overall measured rates of reactions and not enzyme catalytic properties

Question 9

Feedback Inhibition

Answer 9

This is the phenomenon by which the final metabolite of a pathway inhibits the synthesis of an enzyme, usually the first one

Question 10

What is an example of feedback inihbition?

Answer 10

Rate-limiting step where final product of the pathway behave as an inhibitor for it

Question 11

What is an example of feedback inhibition?

Answer 11

3-phosphoglycerate dehydrogenase

Question 12

phosphoglycerate dehydrogenase

Answer 12

This is the first commited enzyme in the serine synthesis pathway

Question 13

What is the structure of 3-PGD

Answer 13

Tetramer of 4 identical subunits with 4 catalytic site and 4 regulatory serine-binding sites

Question 14

Allosteric Regulation

Answer 14

This is where protein functional activity is altered by the binding of an effector at an allosteric site that is topograhpically distinct from the active site

Question 15

What is allosteric regulation associated with often?

Answer 15

Multi-subunit enzymes with positive and negative regulators

Question 16

Co-operative Binding

Answer 16

THis occurs if the number of binding sites of a macromolecules that are occupied by specific type of ligand is a nonlinear function of the ligands concentration

Question 17

How does allosteric regulation relate to MMK?

Answer 17

S is sigmoidal as substrate binding to one site decreases the Km at other active sites resulting in rapid response to increased S

Question 18

What is the sigmoidal allosteric plot related to?

Answer 18

T state and R state of their enzymatic activity

Question 19

What does switch from T to R do>?

Answer 19

Decrease Km and increase reaction rate

Question 20

What is an example of allosteric regulation?

Answer 20

Aspartate Carbamoyltransferase

Question 21

Aspartate Carbamoyltransferase

Answer 21

This is a transaminase enzyme catalysing conversion of aspartate and alpha-ketoglutarate to oxaloacetate tand glutamate

Question 22

Where is ACT used?

Answer 22

First commited step in pyrimidine synthesis where endpoints are cytidine triphosphate

Question 23

What does cytidine triphosphate transform ACT to?

Answer 23

From a relaxed state to Tense state

Question 24

What is ACTase activity inhbiited by?

Answer 24

Presence of CTP

Question 25

Iso\ymes

Answer 25

These are alternative forms of the same enzyme activity existing in different proportions in different tissue

Question 26

What does the different enzymatic activity of isozymes mean?

Answer 26

Different Km and Vmax

Question 27

What are isozymes encoded by?

Answer 27

Gene families

Question 28

What is an example of isozymes?

Answer 28

LDH conversion of lactate to pyruvate

Question 29

What are the two forms of LDH?

Answer 29

H Form
M Form

Question 30

H Form

Answer 30

This is found in the heart with higher affinity, can be inhibited by pyruvate with optimization to conversion of lactate to pyruvate for aerobic

Question 31

M Form

Answer 31

This is found in skeletal muscles with faster catalysis, optimised to pyruvate to lactate conversion in glycolysis