Lec 9 - Understanding IGPD

Question 1

What are the functional requirements of herbicides to allow for them to be applied to no-till agriculture?

Answer 1

• have to be deactivated upon soil contact - have to kill the weeds

Question 2

How does Glyphosate kill weeds and why is it an effective herbicide?

Answer 2

• inhibits the Shikimate pathway - becomes deactivated on contact w/ soil when binds to cations - cheap

Question 3

Why do we need to look for new herbicide targets such as IGPD?

Answer 3

build of resistance by weeds against heribicide

Question 4

Describe the enzyme IGPD

Answer 4

• v large - 24 subunit (many gene duplication events) - assembled into trimers that each bind 2 Mn ions

Question 5

The N atoms of the ______ ring of IGP coordinate the __ ion.

Answer 5

imidazolate Mn

Question 6

Describe Form A of IGPD

Answer 6

binds neutral IGP (imidazole ring is normal - one N is protonated the other is not)

can see in diag that one Mn ion is coordinated by 6 molecules, the other one by 5 - energetically unstable

Question 7

Describe Form B of IGPD

Answer 7

binds the imidazolate anion of IGP

both Mn are now coordinated by 6 molecules

• saying that the energy by the Mn being coordinated by only 5 atoms was used to create this high energy intermediate (unfavourable imidazloate anion)

Question 8

How did both enantiomers of the inhibitor molecule bind to IGPD?

Answer 8

mirror image packing - one of the binding sites was not filled