PDH Basics
This molecule is produced by Pyruvate Dehydrogenase Complex (PDH) and enters the Citric Acid Cycle.
Acetyl-CoA
This vitamin B1 derivative is required by E1.
Thiamine Pyrophosphate (TPP)
This enzyme phosphorylates PDH and turns it off.
Pyruvate Dehydrogenase Kinase
This molecule combines with acetyl-CoA to begin the cycle.
Oxaloacetate
This reaction generates GTP through substrate-level phosphorylation.
Succinyl-CoA synthase reaction
This enzyme performs oxidative decarboxylation of pyruvate.
E1 (Pyruvate Dehydrogenase)
This cofactor functions as a flexible swinging arm between active sites.
Lipoamide
This enzyme removes the phosphate and activates PDH.
Pyruvate Dehydrogenase Phosphatase
This enzyme catalyzes the first step of the cycle.
Citrate synthase
How many NADh molecules are produced per turn of the Citric Acid Cycle?
3 NADH
This enzyme transfers the acetal group to CoA.
E2 (Dihydrolipoyl Transacetylase)
This cofactor forms a high-energy thioester bond that captures the acetyl group before it enters the Citric Acid Cycle.
Coenzyme A
High concentrations of ATP, NADH, and acetyl-CoA have what effect on the Pyruvate Dehydrogenase?
They inhibit PDH by activating PDH kinase
This enzyme rearranges citrate into isocitrate through dehydration followed by hydration.
Aconitase
How many FADH2 molecules are produced per turn of the Citric Acid Cycle?
1 FADH2
This enzyme regenerates oxidized lipoamide.
E3 (Dihydrolipoyl Dehydrogenase)
The two cofactors participate in electron transfer during regeneration of lipoamide.
FAD and NAD+
These two molecules inhibit PDH kinase.
ADP and pyruvate
This enzyme performs the first oxidative decarboxylation in the cycle.
Isocitrate Dehydrogenase
During which two reactions are carbon dioxide molecules released in the Citric Acid Cycle?
The isocitrate dehydrogenase reaction and the α-ketoglutarate dehydrogenase reaction
This inherited disorder causes lactic acidosis because pyruvate cannot efficiently become acetyl-CoA.
Pyruvate Dehydrogenase Complex Deficiency
Name the five cofactors required by PDH.
TPP, Lipoamide, CoA, FAD, NAD+
Why is the Pyruvate Dehydrogenase Complex often called the ‘gatekeeper’ of the Citric Acid Cycle?
Because it controls whether pyruvate can enter aerobic metabolism as acetyl-CoA
This enzyme participates in both the Citric Acid and the Electron Transport Chain.
Succinate Dehydrogenase
This vitamin deficiency reduces activity of both PDH and α-ketoglutarate dehydrogenase?
Thiamine (Vitamin B1) deficency