10.4-10.5 Regulation of Citrate Cycle Flashcards
What enzymes correspond with CC regulation?
Pyruvate dehydrogenase, citrate synthase, isocitrate dehydrogenase, a-ketoglutarate dehydrogenase, pyruvate carboxylase
Pyruvate dehydrogenase regulation governed by…?
Regulation governed by energy charge
What happens to inhibit pyruvate dehydrogenase?
Kinase phosphorylates Ser on E1
What happens to activate pyruvate dehydrogenase?
phosphatase removes that phosphate on Ser on E1
Why does calcium inactivate pyruvate dehydrogenase kinase?
Leads to muscle contraction
Let dehydrogenase work to continue the citric acid cycle
What enzyme regulates E1 of pyruvate dehydrogenase?
Pyruvate dehydrogenase kinase
What are the activators of pyruvate dehydrogenase kinase?
ATP, Acetyl CoA, NADH
What are the inhibitors of pyruvate dehydrogenase kinase?
NAD+, CoA, ADP, Calcium
What activates pyruvate dehydrogenase phosphatase 1?
Calcium
What are the irreversible reactions of CC?
1, 3, 4
What kind of things regulate the CC?
substrate availability, energy charge, feedback inhibition, NADH/NAD+ ratio, calcium concentration, succinyl-coA (GTP production)
What activates pyruvate dehydrogenase?
NAD+, CoA, ADP, Calcium (reactants)
What inhibits pyruvate dehydrogenase?
NADH, acetyl coa, ATP (products)
What activates citrate synthase?
ADP
What inhibits citrate synthase?
NADH, citrate, ATP, succinyl-coa
What are the activators and inhibitors of isocitrate dehydrogenase?
Activators - ADP and calcium
Inhibitors - NADH and ATP
What activates and inhibits a-ketoglutarate dehydrogenase?
Activates - AMP, calcium
Inhibits- NADH, succinyl-CoA, ATP
What is Citric acid used for?
commercial food preservative, isolated from lemons
How do you Maximize citrate production?
Experimental setup
Culture conditions inhibit:
* Reactions 2-8
* Citrate lyase
Mold strain with high capacity for citrate export out of the mitochondria and then inhibited reformation of acetyl CoA
What is the Importance of citrate cycle? (3)
-Citrate cycle generates redox power by oxidizing acetyl -CoA– Reduces NAD+ & FAD
-Provides precursors for many other pathways
-Intermediates are shared by other pathways
Name two useful intermediates of the CC?
a-ketoglutarate and citrate
What is a-ketoglutarate used for?
glutamate synthesis
Reductive amination reaction
Reducing power comes from NADH
Glu is precursor for other AAs
What is citrate important for?
Exported to cytosol
* Citrate lyase
* Used to make acetyl-CoA:
– Precursor for fatty acid and cholesterol synthesis
How is acetyl coA transported?
Via citrate; citrate lysis to free acetyl CoA (citrate shuttle)
What kind of pathway is the CC?
amphibolic pathway
– Functions as both a catabolic and anabolic pathway
– Reactions replenish CC intermediates
What two substrates of the CC can leave the mitochondria?
pyruvate and citrate
What do high-energy molecules do?
Inhibit the citric acid cycle
