Other Enzyme Info

Question 1

What is Phosphorylation?

Answer 1

Phosphorylation can activate or inactivate enzymes by causing conformational changes in the protein structure, thereby influencing its activity.

Question 2

What are the three amino acids that phosphorylation focuses on?

Answer 2

Serine (Ser), Threonine (Thr), and Tyrosine (Tyr)

Question 3

Where does phosphorylation typically occur?

Answer 3

On the hydroxyl groups of amino acids

Question 4

Where does the phosphoryl group come from?

Answer 4

The phosphoryl group that is added to the enzyme usually comes from ATP

Question 5

What are Kinases and Phosphatases?

Answer 5

Kinases are responsible for adding phosphoryl groups to proteins. Phosphatases are responsible for removing phosphoryl groups from proteins, reversing the action of kinases.

Question 6

What are Zymogens?

Answer 6

Zymogens are inactive enzyme precursors that can be activated by the cutting of specific peptide bonds

Question 7

Why are Zymogens synthesized in an inactive form?

Answer 7

To prevent premature activity

Question 8

What are the benefits of Zymogens?

Answer 8

Since they are stored in an inactive form, they can be activated at any time necessary
There is also a cascade effect as when one Zymogen is activated it is more likely for another to be activated

Question 9

How does Chymotrypsinogen behave as a Zymogen?

Answer 9

Chymotrypsinogen is a single polypeptide chain that is cross-linked by disulfide bonds. The first cleave comes from trypsin and the second comes from itself to turn into chymotrypsin (The active form)

Question 10

What are the natural substrates for chymotrypsin?

Answer 10

The natural substrates of chymotrypsin are proteins or peptides

Question 11

What is p-Nitrophenyl acetate?

Answer 11

p-Nitrophenyl acetate is a synthetic substrate commonly used in laboratory studies of chymotrypsin because p-nitrophenyl acetate is hydrolyzed is is yellow

Question 12

What are the two phases of Chymotrypsin’s reaction?

Answer 12

Acylation Phase: This is the first step, where the substrate binds to the enzyme (C-terminal fragment is produced)
Deacylation Phase: Water attacks the acyl-enzyme intermediate, breaking the bond, and releasing the second product (N-terminal fragment)

Question 13

What is the catalytic triad of Chymotrypsin?

Answer 13

Serine 195: Nucleophile that attacks the peptide bond. (Nucleophile)
Histidine 57: General acid-base catalyst that activates serine and water (Proton Holder)
Aspartate 102: Stabilizes the histidine, facilitating proton transfers. (Stabalizer)

Question 14

What are the 6 classes of enzymes?

Answer 14

Oxidoreductases
Transferases
Hydrolases
Lyases
Ligases
Isomerases

Question 15

What does each class of enzyme catalyze?

Answer 15

Oxidoreductases: Catalyze oxidation-reduction (redox) reactions
Transferases: Transfers functional groups
Hydrolases: Catalyze the hydrolysis of bonds by adding water
Lyases: Catalyze the breaking of bonds
Ligases: Catalyze the joining of two molecules
Isomerases: Catalyze the rearrangement of atoms within a molecule

Question 16

How are enzymes named?

Answer 16

Enzymes are usually named based on the substrate they act upon and the type of reaction they catalyze. (Often ends in -ase)

Question 17

What is acid-base catalysis?

Answer 17

Acid-Base Catalysis: Mechanism that involves proton transfer to accelerate a reaction.

Question 18

What is metal-ion catalysis?

Answer 18

Metal-Ion Catalysis: Involves metal ions acting as Lewis acids to stabilize intermediates or increase nucleophilicity. (Zn, Fe, Mg, and Ca are the most popular ones)

Question 19

What is the difference between absolute and relative enzyme specificity?

Answer 19

Absolute Specificity: Enzymes act on only one specific substrate.
Relative Specificity: Enzymes act on a range of similar substrates.

Question 20

What is Stereospecificity?

Answer 20

It is when enzymes are selective for one stereoisomer, which reflects precise substrate binding.

Question 21

What are Transition State Analogues?

Answer 21

Potent inhibitors that mimic the enzyme’s transition state.

Question 22

What are Abzymes?

Answer 22

Catalytic antibodies that perform enzymatic reactions, induced by transition state analogues. (Antibodies that act like enzymes)

Question 23

What are coenzymes?

Answer 23

Coenzymes are small molecules that assist enzymes in catalyzing reactions. They are not proteins themselves but are required for enzyme activity.

Question 24

What are examples of coenzymes?

Answer 24

Coenzymes can be inorganic metals or organic molecules derived from vitamins.

Question 25

How is NAD+ a coenzyme?

Answer 25

It participates in reactions where it acts as an electron carrier, accepting electrons during oxidation reactions to become NADH.

Question 26

What makes up the structure of NAD+?

Answer 26

Nicotinamide ring: The site of redox activity, where electrons are transferred
Adenine ring: Part of the nucleotide structure.
Two sugar-phosphates: These link the nicotinamide and adenine portions, forming a dinucleotide.

Question 27

What is important about B6 vitamins?

Answer 27

B6 vitamins participate in amino acid biosynthesis

Question 28

What is an Apoenzyme?

Answer 28

It’s an inactive form of an enzyme that requires a cofactor to become a holoenzyme (the active version of an epoenzyme)