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Flashcards in Enzyme Regulation Deck (13):


- ensures metabolic efficiency and simplifies regulation


Regulatory Enzymes

- have special properties leading to regulatory roles in metabolism
- allosteric and covalently modulated enzymes


Allosteric regulation

- 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


Homotropic allosteric regulator

- a substrate for its target enzyme


Heterotrophic allosteric regulator

- molecule that is not also the enzyme's substrate
- can be activator or inhibitor



-CTP inhibits it, ATP activates it
- binding sites for allosteric modulators are on the regulatory units


Covalent modifications

- 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



- 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


Reversible Acetylation of Proteins at e-AMino Groups of Lys Residues

- 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


Post-translation modification regulation

- rapid
- doesn't require new proteins to be made or degraded
- easily reversible


Glycogen Phosphorylase

- 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


Regulation of Metabolic pathways

- allosteric regulation by ADP/ATP and NAD+/NADH levels
- feedback inhibition
- PTM of metabolic enzymes


Regulation of Enzyme activities by proteolysis

- 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