Questions and Answers
What effect does pyruvate dehydrogenase complex deficiency have on pyruvate levels?
Which cofactor is required for the enzyme alanine aminotransferase?
What is the major outcome of the TCA cycle per acetyl-CoA?
The buildup of lactate due to pyruvate dehydrogenase complex deficiency leads to which condition?
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Which metabolic pathway does pyruvate carboxylase support?
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Which enzyme facilitates the transition from glycolysis to the TCA cycle?
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Which of the following pathways involves the use of alanine?
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What is the main purpose of ketogenically treating pyruvate dehydrogenase complex deficiency?
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Study Notes
Pyruvate Dehydrogenase Complex Deficiency
- X-linked genetic disorder leading to pyruvate accumulation
- Buildup is converted to lactate via lactate dehydrogenase (LDH) and alanine via alanine aminotransferase (ALT)
- Symptoms include neurologic defects, lactic acidosis, and elevated serum alanine from infancy
- Treatment involves high-fat ketogenic diet or supplementation with lysine and leucine
Pyruvate Metabolism Pathways
- Alanine Aminotransferase (ALT): Requires vitamin B6; transports amino groups to the liver from muscle
- Pyruvate Carboxylase: Requires vitamin B7; produces oxaloacetate for TCA cycle replenishment or gluconeogenesis
- Pyruvate Dehydrogenase (PDH): Requires vitamins B1, B2, B3, B5, and lipoic acid; converts pyruvate to acetyl-CoA, initiating TCA cycle
- Lactate Dehydrogenase (LDH): Requires vitamin B3; facilitates end of anaerobic glycolysis, prevalent in RBCs, WBCs, kidney medulla, lens, testes, and cornea
TCA Cycle Overview
- Pyruvate is converted to acetyl-CoA, producing 1 NADH and 1 CO2
- Each acetyl-CoA entering TCA cycle yields 3 NADH, 1 FADH2, 2 CO2, and 1 GTP, equivalent to 10 ATP (per glucose molecule, double the results)
- TCA cycle reactions occur in the mitochondria and involve irreversible enzyme actions, such as:
- Citrate synthase
- Isocitrate dehydrogenase
- α-Ketoglutarate dehydrogenase complex, which requires the same cofactors as PDH
Additional Metabolic Context
- Pyruvate, a 3-carbon compound, is pivotal in energy metabolism
- Acetyl-CoA (2C) enters the TCA cycle, leading to higher energy yields
- Lactate and alanine pathways play significant roles in cellular metabolism and energy homeostasis
- Cori cycle and Cahill cycle highlight the interplay between lactate production and amino acid metabolism, emphasizing the adaptive nature of energy production in various tissues
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Description
Explore the causes, effects, and treatments of Pyruvate Dehydrogenase Complex Deficiency. This quiz covers key findings such as neurologic defects, lactic acidosis, and dietary recommendations. Test your knowledge on pyruvate metabolism and its pathways.
