Enzymes

Question 1

Give function and examples of oxidoreductases.

Answer 1

• Move electrons

- NADH, NADPH, FADH2, FMNH

Question 2

Give function and examples of Transferases.

Answer 2

• Move a functional group

- ATP, SAM, Pyridoxal phosphate, 5’-deoxy…, tetrahydrofolate

Question 3

Give function hydrolases.

Answer 3

• Break chemical bonds via hydrolysis

Question 4

Give function of isomerase.

Answer 4

Rearrange order of atoms in a molecule

Question 5

Give function of lyases.

Answer 5

Break a chemical bond w/out water

Question 6

Give function and examples of ligases .

Answer 6

• Make chemical bond using ATP

- TPP, CoASH, Lipoamide, biotin

Question 7

What are characteristics of an active site?

Answer 7

1. Is only a few residues out of the protein
2. Is a 3-D cleft/crevice/pocket, creating a unique microenvironment
3. Determines substrate specificity by size and charge complementarity 4. Contacts with the substrate through noncovalent interactions

Question 8

What is characteristic of allosteric binding?

Answer 8

1. Does NOT occur at the active site, but follows the same interaction rules as an active site
2. Involves a second substrate, which can be an activator or an inhibitor

Question 9

Compare and contrast Apo and Holoenzymes

Answer 9

Apoenzymes:
• Incomplete
• Inactive
• Lack cofactor/coenzyme

Holoenzymes: 
• Whole 
• Active 
• Contain cofactor/coenzyme 
• Require allosteric activation!

Question 10

What is Y and how is it calculated?? What are possible values for Y and what they mean?

Answer 10

Fractional saturation Y = [E-S]/[E]+[E-S]
= [S]/KD+[S]

Y = 0 - no ligand bound
Y = 0.5 - half saturated
Y = 1 - saturated

Question 11

What is cooperativety?

Answer 11

Binding of each subsequent ligand influences the affinity (strength of interaction) of the next ligand to bind an active site

Question 12

How do we interpret cooperativity?

Answer 12

In terms of cooperativity, we interpret Hill Coefficients in the following way:
• nH = 1 means nocooperativity
(sites are independent)
• nH > 1 means positivecooperativity
(affinity increases)
• 0 < nH < 1 means negativecooperativity
(affinity decreases)