Redox Reactions II

Question 1

What enzyme makes hydrogen peroxide into hypochlorous acid?

Answer 1

Myeloperoxidase

Question 2

How are ROS involved in phagocytosis?

Answer 2

• NADPH oxidase is assembled following phagocytosis
• Produces superoxide
• Superoxide dismutates into peroxide which is then used to form hypochlorous acid

Question 3

What cofactor does myeloperoxidase contain?

Answer 3

Heme

Question 4

Which types of cells is myeloperoxidase present in in high concentration?

Answer 4

Neutrophils

Question 5

What oxidation states can the iron of heme be in?

Answer 5

+2, +3, +4

Question 6

What can the interaction of a photosensitiser and light do to oxygen?

Answer 6

flip thespin of an electron of oxygen to produce singlet oxygen

Question 7

Where does singlet oxygen esepcially react?

Answer 7

at double bonds

Question 8

What is the basis for photodynamic therapy?

Answer 8

If singlet oxygen can be selectively generated at a local site, then tissue can be selectively damaged/destroyed

Question 9

Besides photosensitisers how can electron spin pairing in oxygen be achieved?

Answer 9

Using heat

Question 10

How does photodynamic therapy work?

Answer 10

• Photosensitisers targeted to area want to damage
• Use red light on the area
• High intensity laser light is applied

Question 11

When type of light is mostly absorbed by photosensitisers?

Answer 11

Red light

Question 12

What is the usual structure for photosensitisers?

Answer 12

Porphyrin-like molecules

Question 13

Why is it important to be able to sense low oxygen conditions?

Answer 13

To prevent hypoxia-induced damage

Question 14

Under normal conditions what happens to HIF?

Answer 14

It is targeted for degradation

Question 15

How is HIF targeted for degradation?

Answer 15

• PHD 2 and 3 selectively hydroxylate part of HIF in prescence of oxygen
• Once proline is hydroxylated an E3 ubiquitin ligase recognises the HIF and targets protein for degradation

Question 16

What happens to HIF in hypoxic conditions?

Answer 16

• The hydroxlyase is no longer able to hydroxylate HIF and HIF binds to p3100
• HIF binds to DNA and activates transcription of vital genes for hypoxia

Question 17

Give an example of a gene which might be activated in hypoxic conditions

Answer 17

Gene for EPO

Question 18

What general structure do prolyl hydroxylases have?

Answer 18

Non-heme iron containing enzymes with a jelly roll (mixed alpha/beta-fold)

Question 19

What does the catalysis of prolyl hydroxylases rely on?

Answer 19

• Oxygen
• Alpha ketoglutarate
• Water

Question 20

What does the active site of prolyl hydroxylase comprise of?

Answer 20

Non-heme iron ion co-ordinated by a facial triad of Asp-His-his

Question 21

What geometry is the iron in prolyl hydroxylases?

Answer 21

Octahedral

Question 22

What can mutations in iron binding of prolyl hydroxylase result in?

Answer 22

Over-production of red blood cells as it inactivates the enzyme so HIF can bind and increase EPO

Question 23

What are 2 ways bacteria sense O₂ levels?

Answer 23

• FNR Regulon
• FixL

Question 24

How does FNR regulon work?

Answer 24

• When exposed to oxygen the clusters are degraded which prevents dimerisation
• Dimerisation is required for binding to DNA
• With no oxygen the protein can bind to DNA and allow for transcription of low oxygen genes

Question 25

How does FixL work?

Answer 25

• When oxygen isn’t bound it leads to dimerisation and binding to DNA
• Binds to promoters activating anaerobic genes
• Can also repress oxygen dependent pathways