Enzyme Regulation Flashcards
1
Q
Compartmentaltion
A
- ensures metabolic efficiency and simplifies regulation
2
Q
Regulatory Enzymes
A
- have special properties leading to regulatory roles in metabolism
- allosteric and covalently modulated enzymes
3
Q
Allosteric regulation
A
- enzymes are highly regulated by binding small molecules that can either decrease or increase activity
- Feedback inhibition: first enzyme in a multi-step pathway inhibited by the final product of the pathway
- modulator binds non-covalently to site other than active site
- negative modulator inhibit, positive stimulate
4
Q
Homotropic allosteric regulator
A
- a substrate for its target enzyme
5
Q
Heterotrophic allosteric regulator
A
- molecule that is not also the enzyme’s substrate
- can be activator or inhibitor
6
Q
ATCase
A
- CTP inhibits it, ATP activates it
- binding sites for allosteric modulators are on the regulatory units
7
Q
Covalent modifications
A
- regulate metabolic flow by post-translationally modifying key metabolic enzymes and proteins
- occurs by post translational modification of AA side chains
- regulatory modifications: phosphorylation acetylation, methylation, ADP-ribosylation
- Structural modifications: Prenylation, glycosylation, hydroxylation, and FA acylation
- Proteolysis - irreversible
8
Q
Phosphorylation
A
- reversible
- introduces 2 negative charges on proteins
- kinases add a phosphate to hydroxyl side chains
- phosphatase so remove a phosphate from a phosphorylated side chains
9
Q
Reversible Acetylation of Proteins at e-AMino Groups of Lys Residues
A
- acetylation neutralizes the positive charges on Lys residues
- sirtuins - involved in deacetylation
- SIRT1 - nucleus
- SIRT3 - mitochondria, is the major mitochondrial NAD+ dependent deacetylase involved in tumors suppression as well as many other physiological processes
10
Q
Post-translation modification regulation
A
- rapid
- doesn’t require new proteins to be made or degraded
- easily reversible
11
Q
Glycogen Phosphorylase
A
- activity of glycogen phosphorylase involves covalent modification, allosteric regulation, and a regulatory cascade sensitive to hormonal status that acts on the enzymes involved in phosphorylation an dephosphorylation
12
Q
Regulation of Metabolic pathways
A
- allosteric regulation by ADP/ATP and NAD+/NADH levels
- feedback inhibition
- PTM of metabolic enzymes
13
Q
Regulation of Enzyme activities by proteolysis
A
- irreversible
-near ubiquitous - rapid mobilization of an activity in response to physiologic demand
-Met excision
-signal peptide removal during translocation of a protein
-N and C terminal processing proteins into their active forms
Ex blood coagulation cascade and zymogens