Lecture 12: Enzymes III- Regulation Flashcards
Substrate-level control
Acts as a SINGLE reaction
Feedback control
Targets a different step in the pathway
What is the effect on product formation?
- Activators PROMOTE more products
- Inhibitors PREVENT more products
Enzyme Regulation
- Regulate the amount or availability (on/off)
2. Regulate the activity of the enzyme (volume control)
Regulate the amount or availability (enzyme reg)
- Temporal control of gene expression
- Protein Degradation
- Enzyme Compartmentalization
- Substrate Availability
Regulate the activity of the enzyme (enzyme reg)
- Isozymes and isoforms
- Covalent modifications
- Allostery
Enzyme Compartmentalization
- Act in a specific location
- -> Can control how much E + S (reg how available)
Substrate Availability
How is substrate coming and getting into cell
-Signaling cascade
Isozymes and Isoforms
*Catalyze the SAME reaction but with DIFFERENT efficiences
-Not a clear destination
-“Mix and Match” subunits:
Paralogs, alt splicing, heterozygous alleles, monomer vs dimer/trimer, +/- covalent modifications and conformations
Compartmentalized isozymes
Results in tissue specificity
Temporal expression of isozymes
Common in development
Lactate Dehydrogenase (LDH)
Participates in the lactic acid fermentation pathway
-LDH=tetramer : isoforms say where expressed (heart or sk muscle)
LDH1=H4
Had a MI
LDH5=M4
Liver is damaged
Covalent modifications
Phosphorylation, acetylation, myristoylation, ADP ribosylation, farnesylation, gamma-carbox. sulfation, ubiquit
Reversible Covalent Modifications
Lipids (myristic acid= fatty acid)
Farnesyl (intermediate in cholesterol synthesis)
Nucleic acids (ADP-ribose)
Proteins (Ubiquitin)
Small molecules- gamma carboxylation, sulfation, acetylation and methylation, phosphorylation (off of hydroxyl)
Reversible covalent modifications - Carboyhydrates
The greatest source of diversity to the proteome!
- O vs N-linkages
- Composition of sugars
- Branched vs unbranched
- Length of oligosaccharide
What is phosphorylation activating?
- Thermodynamics - ATP hydrolysis can drive unfavorable reactions (delta G=50 kJ/mol)
- Kinetics- Phys processes dictate reaction rate (msec-hrs/rxn)
- Cell processes - APT amounts dictacted by metabolism (energy charge) and signal transduction amplification (catalytic turnover)
- Shape and Charge Complementarity- each phosphate adds (-2) charge and (+3) H-bonds
Kinases
ADD phosphate
[Name of kinase indicates on which AA the phosphate will be add]
Phosphates
REMOVE phosphates
Covalent Modifications: Irreversible
Proteolytic activation (Cleaves to activate)
Proteases
[Many enzymes begin life as ZYGOMENS- need to be cleaved to be activated] –Digest enzymes, Collagenous (Development), Caspases (Apoptosis)
- Collagen
- Blood clotting factors
- Insulin/H’s
Allosery
- Heteroallostery - Effector binds at the allosteric site (Enzyme to other)
- Homoallostery - Cooperativity (Enzyme to itself)
Binding of CTP
Prefers the T/inactive state
“Tense state”
Binding of ATP
Prefers the R/active state
“Relaxed state”
