Source / episode info
- **Episode:**15
- **Title:**Divine Intervention Episode 15 – Metabolism Review B.
- **Published:**2018-04-03
- Source:Episode page
One-liner
This episode reviews core metabolic pathways, detailing how insulin/glucagon regulate key enzymes (e.g., PFK-1, Pyruvate Kinase), comparing the pathophysiology of galactose and fructose metabolism disorders, and covering oxidative stress mechanisms like NADPH oxidase deficiency and glutathione recycling.
High-yield summary
- Metabolic Regulation: Insulin is a dephosphorylator (activating state); Glucagon is a phosphorylator (inactivating state). This principle applies to key enzymes like Pyruvate Kinase and Acetyl-CoA Carboxylase.
- Galactose vs. Fructose Metabolism: Galactose disorders often present with cataracts due to galactitol accumulation; fructose disorders are generally more severe when the second enzyme is deficient, leading to profound hypoglycemia and liver failure.
- Oxidative Stress: Chronic Granulomatous Disease (CGD) results from NADPH oxidase deficiency, making patients susceptible to catalase-positive organisms (e.g., Staphylococcus, E. coli).
- Glucose Transporters: GLUT1 has a low K_M and is found in the brain/red cells; GLUT2 has a high K_M, is bidirectional, and functions as a glucose sensor in the liver/pancreas -cells.
- Glycolysis Control Point: The rate-limiting step catalyzed by PFK-1 is allosterically activated by Fructose-2,6-bisphosphate, which itself is regulated by insulin via the PFK-2 bifunctional enzyme complex.
Learning objectives
- Differentiate the metabolic consequences and clinical presentations of galactosemia versus fructose intolerance.
- Describe the enzymatic cascade involved in oxidative burst and identify deficiencies leading to immunodeficiency (CGD).
- Explain the allosteric regulation of key glycolytic enzymes, particularly PFK-1 and Pyruvate Kinase.
- Correlate amino acid metabolism defects (e.g., PKU) with cofactor requirements (\text{BH}_4).
- Differentiate between glucose transporters (GLUT1 vs. GLUT2) based on K_M and tissue distribution.
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