Biochem PDH Complex

What is the main fate of pyruvate?

pyruvate dehydrogenase complex (PDH complex)

Where is the PDH complex located?

mitochondrial matrix

What type of reaction is the PDH complex reaction?

catabolic reaction

What are the steps of the synthesis of acetyl CoA from pyruvate?

decarboxylation, oxidation, transfer to CoA

What is the E1 enzyme in the PDH complex?

pyruvate dehydrogenase component

What is the prosthetic group of the E1 enzyme?

TPP

What is the reaction catalyzed by the E1 enzyme?

oxidative decarboxylation of pyruvate

What is the E2 enzyme of the PDH complex?

dihydrolipoyl transacetylase

What is the E3 enzyme of the PDH complex?

dihydrolipoyl dehydrogenase

What is the prosthetic group of the E2 enzyme?

lipoamide

What is the reaction catalyzed by the E2 enzyme?

transfer of acetyl group to CoA

What is the prosthetic group of the E3 enzyme?

FAD

What is the reaction catalyzed by the E3 enzyme?

regeneration of the oxidized form of lipoamide

What does phosphorylation do to the PDH complex?

turns it off

What are acetyl CoA and NADH to the PDH complex?

products and allosteric inhibitors

What does low energy charge do to the PDH complex?

stimulate it

Where does acetyl CoA go after the PDH complex?

the citric acid cycle

What type of reaction is the citric acid cycle?

amphibolic, main cycle is catabolic but intersects with anabolic pathwaysW

Where does the citric acid cycle take place?

the mitochondrial matrix

How many turns of the citric acid cycle are there per glucose?

2AT

What are allosteric inhibitors of the citric acid cycle?

ATP and NADH

Does the TCA cycle change the net concentration of oxaloacetate in the cell?

no because it is recycled

What does a high acetyl-CoA concentration mean?

not enough oxaloacetate, can’t be made into citrate

What is the only enzyme that can catalyze the formation of oxaloacetate?

pyruvate carboxylase

What are the irreversible steps of the citric acid cycle?

1,3,4

What increases in concentration due to PDH complex deficiency?

pyruvate and lactate

When does pyruvate convert to lactate?

low O2 or metabolic deficiency

What enzyme catalyzes the formation of lactate from pyruvate?

lactate dehydrogenase

What is the purpose of the remaining steps of the PDH complex after releasing acetyl CoA?

regenerate oxidized form of lipoyl group

What are catalytic coenzymes?

those that are not consumed in the reaction

What are the catalytic coenzymes in the PDH complex?

TPP, lipoic acid, FAD

What are stoichiometric coenzymes?

those used as substrates

What are the stochiometric coenzymes in the PDH complex?

CoA, NAD+

What do the NADH and FADH2 produced by the citric acid cycle do?

relay electrons extracted from food to the electron transport chain

What is the enzyme of step 4 of the citric acid cycle similar to?

the PDH complex, same cofactors, E3 identical, also affected by complex deficiency

What are the fates of oxaloacetate?

combine with acetyl CoA to form citrate, used to form glucose in gluconeogenesis, forms aspartate which forms other amino acids, purines, and pyrimidines

What enzyme regulates step 1, acetyl CoA + oxaloacetate —→ citrate, of the citric acid cycle?

citrate synthase

What happens to oxaloacetate when energy charge is high?

anabolic pathways decrease amount of oxaloacetate in the cell

What happens to oxaloacetate when energy charge is low?

rate of TCA cycle increases: need more oxaloacetate

Where is pyruvate converted to lactate?

cytoplasm

What are problems caused by PDH complex deficiency?

lactic acidosis, hyperventilation, muscle pain and weakness, abdominal pain, and nausea

Is the citric acid cycle completely stopped when there is PDH complex deficiency?

no