Enzyme Regulation Flashcards
How does compartmentation help with enzyme regulation?
Keeps enzyme and substrates in specific compartments so that reactions do not accidentally happen
E.g.: FA synthesis in cytosol and oxidation in mitochondria
On a Michaelis Menten curve, where is the best place to regulate an enzyme?
Near the Km value, linear portion of curve
Feedback inhibition is a type of _____ regulation.
allosteric
In feedback inhibition, how is the first enzyme in a pathway regulated?
The first enzyme is regulated by the last product
What are oligomeric enzymes?
Enzymes with multiple binding sites for regulators
E.g.: could have a site for inhibition for citrate and an activation site for ADP
The homotropic allosteric regulator is the same as the ____ for the enzyme. This means the homotropic regulator is more likely (activating/inactivating) the enzyme.
substrate, activating
T/F. The heteroropic allosteric regulator can be either the enzyme substrate or another ligand
False.
Heterotropic is not the enzyme substrate, but homotropic is.
Are hetertropic allosteric regulators activators, inhibitors, or both for enzymes?
Can be both
T/F. Allosteric modulation can only occur with enzymes that do not follow a Michaelis Menten curve.
True
Aspartate transcarbamoylase (ATCase) is an ______ enzyme with multiple binding sites for inhibitors and activators. It is active in ___ ___. The inhibitor is _____, and the activator is _____.
oligomeric, DNA synthesis, CTP, ATP
What are the two types of post translational modifications?
Regulatory and structural
Proteolysis is an ______ modification
irreversible
What are the three benefits of post translational modifications as opposed to modifications during protein synthesis?
Rapid, does not need to happen from beginning of complex protein synthesis process, reversible
Which enzymes phosphorylate? Which enzymes dephosphorylate?
Kinases, phosphatases
Kinases phosphorylate the ___ groups on __, ___, and ___.
OH groups on Ser, Thr, Tyr
Molecularly, how does phosphorylating a structure regulate the enzyme?
Changing an uncharged polar to a negatively charged structure with the addition of phosphate
Tyrosine kinase activity is inhibited in cancer treatment via _____ of the enzyme.
phosphorylation
What percentage of our proteins are regulated by phosphorylation?
70%
Why do enzymes requiring ATP also require Mg (2+)?
The magnesium stabilizes the two phosphates closest to the enzyme (farther away from the adenosine) and prevent the negatively charged phosphate groups from repelling each other
What amino groups are acetylated?
epsilon (meaning not the alpha carbon amino group) amino groups of Lys
How does acetylation of Lys affect the molecular structure of the enzyme?
The acetylation neutralizes the Lys positive charge
What enzyme participates in Lys acetylation? What enzyme removes acetylation?
lysine acetyltransferases, NAD+ dependent deacetylases
_____ is a NAD+ dependent deacetylase involved in tumor suppression, heart protection, FA oxidation, thermogenesis, and mitochondrial biogenesis.
SIRT3
What are two methods of inhibiting metabolic pathways?
Allosteric (like feedback inhibition) and post translational modification.
For example, could phosphorylate an enzyme with ATP cleavage, or the end product of a metabolic pathway could inhibit the first enzyme.
What is an example of allosteric regulations used in metabolic pathways?
ADP/ATP and NAD+/NADH concentrations.
E.g. high energy vs. low energy states in the TCA cycle
What are three methods of proteolysis?
Met residue excision after translation
Signal peptide cut out during translocation
N and C terminal processing of proteins into their active forms (e.g. blood coagulation)
Four ways to regulate enzymes.
Compartmentation, allosteric, covalent (includes regulatory PTMs, structural PTMs, and proteolysis which is irreversible), association with a regulatory protein
Where does ATP bind to on an ACTase?
regulatory subunit
Structural modifications?
hydroxylation, prenylation, glycosylation, FA acylation
