Lecure 14- regulation of protein function

Question 1

What can be noted about enzymes in protein formation?

Answer 1

Changing enzyme activity in pathway changes how the pathway works

Question 2

What are isoenzymes?

Answer 2

Different forms of the same enzyme that have different properties

Question 3

What is a co-enzyme?

Answer 3

Non-protein compound necessary for the functioning of an enzyme

Question 4

What is interesting about allosterically regulated enzymes?

Answer 4

Show a sigmoidal relationship because of two different conformations (t and r state)

Question 5

How can allosteric inhibitor affect enzyme?

Answer 5

Can lower Vmax as it is a non competitive inhibitor

Question 6

Give an example of an allosterically regulated enzyme?

Answer 6

Phosphofructokinase. Inhibited by ATP, citrateand H+. More of enzyme in T state. Activated by AMP and fructose 2-6 bisphosphate

Question 7

What enzymes add phosphate and what enzymes remove phosphate?

Answer 7

Protein kinase adds phosphate and protein phosphates removes phosphate

Question 8

What’s good about phosphorylation (covalent modification)

Answer 8

Adds to negative charges

Can make H bonds

Rate of phosphorylation/dephosphorylation can be adjusted

Links energy status of cell to metabolism through ATP

Allows for amplification effects

Question 9

What is an enzyme cascade?

Answer 9

Enzyme amplification process

Question 10

Interesting about glycogen mobilisation?

Answer 10

Synthesis and breakdown are reciprocally regulated

Question 11

What is a zygotes?

Answer 11

Inactive substance converted into an enzyme when proteolytic ally cleaved by an enzyme

Question 12

Give an example of an enzyme activated by proteolytic cleavage?

Answer 12

Digestive enzymes synthesised as zymogens eg pepsinogen to pepsin.

Chymotrypsinogen to chymotrypsin

Question 13

How do we control enzymes?

Answer 13

Degradation

Irreversibly bind inhibitor

Question 14

Alpha 1 antitrypsin deficiency?

Answer 14

Inhibits a range of proteases one of which is elastase.

Deficiency means continued action of elastase. Breaks down elastin in alveoli== emphysema

Question 15

Long term protein regulation?

Answer 15

Changing gene expression

Can change rate of protein synthesis through enzyme induction or repression

Can change rate of protein degradation through ubiquitous proteosome pathway

Question 16

Important point about clot formation?

Answer 16

It is an amplification cascade

Question 17

Role of g-carboxyglutamate residues in clot formation?

Answer 17

Responds to calcium present at site of damage. Brings clotting factors site

Question 18

Structure of fibrinogen?

Answer 18

Has negative charges and globular units at ends to prevent aggregation

Question 19

What causes classic haemophilia?

Answer 19

A defect in factor VIII of the clotting cascade

Question 20

What is interesting about thrombin in the clotting cascade?

Answer 20

It makes the cascade a feed forward mechanism

Question 21

How is clotting process stopped?

Answer 21

Dilution of clotting factors by blood flow and removal by liver

Digestion by proteases

Specific inhibitors

Question 22

What points of blood clot formation can be regulated?

Answer 22

Inactive zymogens low concentration

Proteolytic activation

Amplification (signal cascade)

Clustering of factors at damage site

Feedback activation by thrombin

Termination of clotting mechanisms

Clot breakdown controlled by proteolytic activation

Question 23

Regulating enzyme activity?

Answer 23

Short term:

Substrate and product concentration

Changing enzyme conformation (allosteric, covalent modification, proteolytic cleavage)

Long term regulation
Change rate of protein synthesis and degradation

Question 24

What drug works on the clotting cascade?

Answer 24

Warfarin- prevents blood clots