Enzyme Regulation

Question 1

How does compartmentation help with enzyme regulation?

Answer 1

Keeps enzyme and substrates in specific compartments so that reactions do not accidentally happen
E.g.: FA synthesis in cytosol and oxidation in mitochondria

Question 2

On a Michaelis Menten curve, where is the best place to regulate an enzyme?

Answer 2

Near the Km value, linear portion of curve

Question 3

Feedback inhibition is a type of _____ regulation.

Answer 3

allosteric

Question 4

In feedback inhibition, how is the first enzyme in a pathway regulated?

Answer 4

The first enzyme is regulated by the last product

Question 5

What are oligomeric enzymes?

Answer 5

Enzymes with multiple binding sites for regulators

E.g.: could have a site for inhibition for citrate and an activation site for ADP

Question 6

The homotropic allosteric regulator is the same as the ____ for the enzyme. This means the homotropic regulator is more likely (activating/inactivating) the enzyme.

Answer 6

substrate, activating

Question 7

T/F. The heteroropic allosteric regulator can be either the enzyme substrate or another ligand

Answer 7

False.

Heterotropic is not the enzyme substrate, but homotropic is.

Question 8

Are hetertropic allosteric regulators activators, inhibitors, or both for enzymes?

Answer 8

Can be both

Question 9

T/F. Allosteric modulation can only occur with enzymes that do not follow a Michaelis Menten curve.

Answer 9

True

Question 10

Aspartate transcarbamoylase (ATCase) is an ______ enzyme with multiple binding sites for inhibitors and activators. It is active in ___ ___. The inhibitor is _____, and the activator is _____.

Answer 10

oligomeric, DNA synthesis, CTP, ATP

Question 11

What are the two types of post translational modifications?

Answer 11

Regulatory and structural

Question 12

Proteolysis is an ______ modification

Answer 12

irreversible

Question 13

What are the three benefits of post translational modifications as opposed to modifications during protein synthesis?

Answer 13

Rapid, does not need to happen from beginning of complex protein synthesis process, reversible

Question 14

Which enzymes phosphorylate? Which enzymes dephosphorylate?

Answer 14

Kinases, phosphatases

Question 15

Kinases phosphorylate the ___ groups on __, ___, and ___.

Answer 15

OH groups on Ser, Thr, Tyr

Question 16

Molecularly, how does phosphorylating a structure regulate the enzyme?

Answer 16

Changing an uncharged polar to a negatively charged structure with the addition of phosphate

Question 17

Tyrosine kinase activity is inhibited in cancer treatment via _____ of the enzyme.

Answer 17

phosphorylation

Question 18

What percentage of our proteins are regulated by phosphorylation?

Answer 18

70%

Question 19

Why do enzymes requiring ATP also require Mg (2+)?

Answer 19

The magnesium stabilizes the two phosphates closest to the enzyme (farther away from the adenosine) and prevent the negatively charged phosphate groups from repelling each other

Question 20

What amino groups are acetylated?

Answer 20

epsilon (meaning not the alpha carbon amino group) amino groups of Lys

Question 21

How does acetylation of Lys affect the molecular structure of the enzyme?

Answer 21

The acetylation neutralizes the Lys positive charge

Question 22

What enzyme participates in Lys acetylation? What enzyme removes acetylation?

Answer 22

lysine acetyltransferases, NAD+ dependent deacetylases

Question 23

_____ is a NAD+ dependent deacetylase involved in tumor suppression, heart protection, FA oxidation, thermogenesis, and mitochondrial biogenesis.

Answer 23

SIRT3

Question 24

What are two methods of inhibiting metabolic pathways?

Answer 24

Allosteric (like feedback inhibition) and post translational modification.
For example, could phosphorylate an enzyme with ATP cleavage, or the end product of a metabolic pathway could inhibit the first enzyme.

Question 25

What is an example of allosteric regulations used in metabolic pathways?

Answer 25

ADP/ATP and NAD+/NADH concentrations.

E.g. high energy vs. low energy states in the TCA cycle

Question 26

What are three methods of proteolysis?

Answer 26

Met residue excision after translation
Signal peptide cut out during translocation
N and C terminal processing of proteins into their active forms (e.g. blood coagulation)

Question 27

Four ways to regulate enzymes.

Answer 27

Compartmentation, allosteric, covalent (includes regulatory PTMs, structural PTMs, and proteolysis which is irreversible), association with a regulatory protein

Question 28

Where does ATP bind to on an ACTase?

Answer 28

regulatory subunit

Question 29

Structural modifications?

Answer 29

hydroxylation, prenylation, glycosylation, FA acylation