MT 3

Question 1

The passing of the intermediary metabolic product of one enzyme directly to another enzyme or active site without its release into solution.

Answer 1

Substrate Channelling

Question 2

Catalyzes the phosphorylation of a specific Ser residue on the E1 subunit of Pyruvate
Dehydrogenase, rendering it inactive

Answer 2

Pyruvate dehydrogenase kinase (PDH kinase)

Question 3

Unsaturated diol that is important intermediate in glycolysis

Answer 3

enediolate; R-C(OH)=C(OH)-R

Question 4

What evidence supports the triose phosphate isomerase reaction proceeding through an enediolate intermediate?

Answer 4

If Lys is changed to Ala in a radiolabel screening, there will be no activity. Reduction of Schiff base from imine to amine prevents electron sink.

Question 5

What evidence supports the triose phosphate isomerase (TIM) reaction proceeding through an enediolate intermediate?

Answer 5

The enediolate transition state analogs bind more tightly to TIM than either the GAP or DHAP substrates

Question 6

How was the GAPDH mechanism elucidated for Step 6?

Answer 6

Modify Cys residue with Iodacetate and the enzyme becomes inactivated. Also, Direct hydride transfer from substrate to NAD+ is confirmed with 3H (as shown by radio labeling).

Question 7

How are glycolysis and the citric acid cycle connected?

Answer 7

A lipoamide is linked to a long flexible chain (Lys) in the 2nd enzyme active site (E2)

Question 8

When this type of molecule binds to an enzyme, all active sites on the protein subunits are changed slightly so that they work less well. They stabilize the T form (=TOO bad), which has a low affinity for its substrate

Answer 8

allosteric inhibitor

Question 9

When this type of molecule binds to locations on an enzyme other than the active site, it causes an increase in the function of the active site. They stabilize the R form (RUN better), which has a high-affinity for its substrate

Answer 9

allosteric activator

Question 10

In this case, the substrate itself serves as an allosteric activator: When it binds to one active site, the activity of another active sites goes up.

Answer 10

Cooperativity

Question 11

replenish intermediates that were diverted from the citric acid cycle for other purposes

Answer 11

Anaplerotic reactions