Lecture 14: Enzyme regulation

Question 1

Describe substrate level control

Answer 1

acts on a single reaction, so A–>B

Question 2

Describe feedback control

Answer 2

acts on different steps in the pathway

Question 3

What are the 5 regulation strategies

Answer 3

1. allosteric control
2. multiple forms of enzymes (isozymes)
3. reversible covalent modification (kinases and phosphorylates)
4. proteolytic activations (zymogens)
5. controlling how much enzyme is present

Question 4

Who are isozymes?

Answer 4

They catalyze the same reactions with different efficiencies because they have different structures

Question 5

Define reversible covalent modifications

Answer 5

they reversible lol

add 1+ functional groups to activate or inactivate the enzyme

includes acetylation, phosphorylation,

Question 6

Describe covalent modifications with lipids

Answer 6

either farnesyl or myristic acid are added

Question 7

Describe covalent modifications with nucleic acids

Answer 7

ADP-ribose

uses NAD+ and NADH

Question 8

Describe covalent modifications in regards to carbohydrates

Answer 8

greatest diversity bc of….

1. O vs N linkage
2. composition of sugars
3. branched vs unbranched
4. length of oligosaccharide

Question 9

Describe the variety of small additions that can occur with covalent modifications

Answer 9

1. gamma carboxylation addition of a three carbon carboxyl group
2. sulfation- PAPS adds a sulfate group to a tyrosine (or threonine/serine)
3. acetylation- acetyl group added
4. methylation- methyl group added
5. phosphorylation- ATP/ADP

Question 10

Describe phosphorylation in terms of what it activates, how it helps the body, and what is needed in order for it to be successful

Answer 10

phosphorylation is the addition of a phosphate group obvi

ATP hydrolysis can drive unfavorable reactions as a lot of energy is given off by removing the phosphate

It can respond to the body’s needs by determining how quickly the body needs the products which is dictated by metabolism (is it anabolic or catabolic)

Needs to have the right shape and charge

Question 11

Describe ATCase

Answer 11

Helps with the first step in the biosynthesis of pyrimidines by taking glutamate and carbamoyl phosphate and adding them together which eventually gets to pyrimidines

Slide 14.20

Question 12

How does CTP effect ATCase?

Answer 12

CTP acts as an allosteric inhibitor and decreases the rate of product formation and prefers the T/inactive state of the ATCase

It binds to the r subunits of the ATCase

Question 13

Describe the structural aspects of ATCase

Answer 13

has regulatory (r) and catalytic (c) subunits that usually form 6 catalytic subunits

Can exist in T and R states

Question 14

Describe ATP’s effect on ATCase and how it effects CTP in the process

Answer 14

ATP is an effector of ATCase, meaning that it stabilizes the R state. It binds to the same area that CTP does, acting as an inhibitor to the CTP, as it doesn’t allow it to access its site (BONUS-what kind of inhibition is this??)

Therefore a higher level of ATP will help to keep the R state of ATCase active

Question 15

Describe the effects of histone

1. acetylation
2. phosphorylation
3. methylation

Answer 15

1. acetylation promotes transcription
2. phosphorylation prevents transcription
3. methylation can either promote or prevent

Question 16

Where does transcription protein synthesis regulation act?

Answer 16

promoters

Question 17

Where does translation protein synthesis regulation act?

Answer 17

UTR’s

Question 18

Describe zymogens

Answer 18

1. Proteases
2. Collagen
3. Blood clotting factors
4. Insulin/hormones

Question 19

Describe the generic regulation strategy exemplified by ATCase

Answer 19

uses allosteric control. The ATCase has distinct regulatory and functional sites and is able to utilize cooperatively

Question 20

Describe the relationship between H4 and M4 LDH

Answer 20

They are isozymes; H is found in the heart and M is found in the skeletal muscle

The H has a high affinity fo rate substrate and is inhibited by high levels of pyruvate; since it is in the heart, it prefers an aerobic environment

The M has not as high of an affinity for the substrate and it works in an anaerobic environment because it has to be hard working

Question 21

Define kinases

Answer 21

phosphorylate molecules; name of the kinase indicates what amino acid is added

Question 22

Define phosphatase

Answer 22

removes phosphates from molecules

Question 23

Describe allostery

Answer 23

allosteric binding does not occur at the active site!
heteroallostery: effector binds at the allosteric site
homoallostery: cooperativity
????

Question 24

Describe how phosphorylation helps the molecules (what does it do?)

Answer 24

1. Thermodynamics- ATP hydrolysis can drive unfavorable reactions
2. Kinetics- physiological processes dictate reaction rate
3. Cell processes- ATP amounts is dictated by metabolism; signal transduction can amplify
4. Shape and Large complimentary: each phosphate adds -2 charge and 3+ h bonds

IN ENGLISH: free energy is at large meaning ATP is easy to get, the phosphryll group adds a negative charge and is able to do a shit ton of H bonds. If the body needs it to be quick, it can be. The effects are able to be HIGHLY amplified

Question 25

Describe the role of proteolytic enzymes in protein regulation

Answer 25

Proteolytic enzymes:
chymotrypsin- leads to the formation of a substrate binding site
trypsin- able to activate a cascade of molecules that is able to lead to a wide variety of interactions which have physiological effects