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What cofactors are used by the pyruvate dehydrogenase complex and what are their origins?
- TPP: Thiamine
- Lipoate
- FAD: Riboflavin
- NAD+: Niacin
- Coenzyme A: Pantahenate
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What are the 3 enzymes found in the PDC?
- Pyruvate Decarboxylase
- Dihydrolipoyl Transacetylase
- Dihydrolipoyl Dehydrogenase
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What 2 regulatory enzymes are used to regulate PDC?
- PDC-Kinase
- PDC-Phosphatase
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How does PDC-Kinase regulate the PDC? What are its activators/inactivators?
- It phosphorylates PDC and thereby inactivates it
- (+) NADH and Acetyl-CoA
- (-) ADP and Pyruvate
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How does PDC-Phosphatase regulate the PDC? What is it regulated by?
- It removes the P group
- Regulated by Calcium
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What happens to the PDC when energy level is high or when the O2 level is low?
It is turned off!
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Describe the severe form of PDC deficiency?
- Severe lactic acidosis at birth
- Death in neonatal period
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Describe the less severe form of PDC deficiency?
- Lactic acidosis moderate at birth
- Psychomotor retardation with increasing age
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Where do the majority of PDC-deficiencies occur?
Alpha subunit of E1
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During what reactions is NADH formed in the TCA?
- Isocitrate --> Alpha-KG (isocitrate DH)
- Alpha-KG --> Succinyl-CoA (Alpha-KG DH)
- Malate --> Oxaloacetate (Malate DH)
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When is FADH2 formed in the TCA?
Succinate --> Fumirate (succinate DH)
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When is GTP formed in the TCA?
Succinyl-CoA --> Succinate (Succinyl-CoA Synth)
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What intermediates from the TCA make AA?
Oxaloacetate and Alpha-KG
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What intermediates from the TCA make FA and sterols?
Citrate
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What intermediates from the TCA go to gluconeogenesis?
Malate
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What intermediates from the TCA make heme groups?
Succinyl-CoA
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What is the main anaplerotic reaction for the TCA cycle?
Pyruvate --> Oxaloacetate (pyruvate carboxylase)
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How is pyruvate carboxylase regulated and what is its main cofactor?
- Main cofactor: Biotin
- Regulation: (+) Acetyl-CoA
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What happens during a pyruvate decarboxylase deficiency?
- Mild-moderate lactic acidemia early in life
- Mental retardation due to glutamine synthesis in brain
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What 3 steps are regulated within the TCA?
- Oxaloacetate --> Citrate (citrate synthase)
- Isocitrate --> Alpha-KG (isocitrate DH)
- Alpha-KG --> Succinyl-CoA (Alpha-KG DH)
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How is citrate synthase regulated in the TCA?
- Oxaloacetate availability
- (-) Citrate, NADH, ATP
- (+) NAD+, ADP
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How is Isocitrate DH regulated in the TCA?
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How is Alpha-KG regulated in the TCA?
- (-) Succinyl-CoA, NADH, ATP
- (+) ADP, Ca++
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What symptoms are seen in a fumirase deficiency and what is elevated?
- Symptoms: Neurological and encephalomyopathy
- Elevated: Fumaric acid, succinate, Alpha-KG, citrate and malate (urine)
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What symptoms are seen in an Alpha-KG deficiency?
- Infantile: Lactic Acidosis
- Childhood: Psychomotor retardation
- Sudden death, myocardiopathy, hepatic disorders
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What symptoms are seen in a Thiamine deficiency and what is it caused by?
- Cause: Chronic alcoholism, dietary
- Symptoms: Inhibition of alpha-KG and PDC
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