Lecture 14: Enzyme regulation Flashcards
Describe substrate level control
acts on a single reaction, so A–>B
Describe feedback control
acts on different steps in the pathway
What are the 5 regulation strategies
- allosteric control
- multiple forms of enzymes (isozymes)
- reversible covalent modification (kinases and phosphorylates)
- proteolytic activations (zymogens)
- controlling how much enzyme is present
Who are isozymes?
They catalyze the same reactions with different efficiencies because they have different structures
Define reversible covalent modifications
they reversible lol
add 1+ functional groups to activate or inactivate the enzyme
includes acetylation, phosphorylation,
Describe covalent modifications with lipids
either farnesyl or myristic acid are added
Describe covalent modifications with nucleic acids
ADP-ribose
uses NAD+ and NADH
Describe covalent modifications in regards to carbohydrates
greatest diversity bc of….
- O vs N linkage
- composition of sugars
- branched vs unbranched
- length of oligosaccharide
Describe the variety of small additions that can occur with covalent modifications
- gamma carboxylation addition of a three carbon carboxyl group
- sulfation- PAPS adds a sulfate group to a tyrosine (or threonine/serine)
- acetylation- acetyl group added
- methylation- methyl group added
- phosphorylation- ATP/ADP
Describe phosphorylation in terms of what it activates, how it helps the body, and what is needed in order for it to be successful
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
Describe ATCase
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
How does CTP effect ATCase?
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
Describe the structural aspects of ATCase
has regulatory (r) and catalytic (c) subunits that usually form 6 catalytic subunits
Can exist in T and R states
Describe ATP’s effect on ATCase and how it effects CTP in the process
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
Describe the effects of histone
- acetylation
- phosphorylation
- methylation
- acetylation promotes transcription
- phosphorylation prevents transcription
- methylation can either promote or prevent
Where does transcription protein synthesis regulation act?
promoters
Where does translation protein synthesis regulation act?
UTR’s
Describe zymogens
- Proteases
- Collagen
- Blood clotting factors
- Insulin/hormones
Describe the generic regulation strategy exemplified by ATCase
uses allosteric control. The ATCase has distinct regulatory and functional sites and is able to utilize cooperatively
Describe the relationship between H4 and M4 LDH
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
Define kinases
phosphorylate molecules; name of the kinase indicates what amino acid is added
Define phosphatase
removes phosphates from molecules
Describe allostery
allosteric binding does not occur at the active site!
heteroallostery: effector binds at the allosteric site
homoallostery: cooperativity
????
Describe how phosphorylation helps the molecules (what does it do?)
- Thermodynamics- ATP hydrolysis can drive unfavorable reactions
- Kinetics- physiological processes dictate reaction rate
- Cell processes- ATP amounts is dictated by metabolism; signal transduction can amplify
- 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
Describe the role of proteolytic enzymes in protein regulation
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
