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Jan 18- Glucose to Pyruvate

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Biomedical Sciences
BMSC 230
Jon Stone

th January 18 , 2011 GLUCOSE TO PYRUVATE Preparatory Phase 1. Hexokinase a. Phosphate comes from hydrolysis of ATP b. Kinase: involved in the transfer of phosphate group c. Hexo: 6 carbon d. Phosphorylates other sugars as well e. Irreversible reaction f. Found in all tissues g. Km = 0.1 mM (concentration at which the enzyme is working at 50% of its velocity) h. G-6-P acts as an inhibitor when the concentration of glucose is high i. Glucose is distributed to the tissues ii. Whatever glucose is left over from the blood it goes to the liver 1. Glucokinase a. Km = 5 mM (can phosphorylate lots of glucose) b. Not inhibited by G-6-P i. Hexokinase = Hexokinase 2 j. Glucokinase = Hexokinase 4 k. In type I diabetics, blood glucose remains high post meal for a long time i. Glucokinase is absent in liver or is not functioning properly ii. Cannot be phosphorylated in liver or stored 2. Phosphohexose Isomerase a. Converts aldose sugar to ketose sugar b. Shift from carbon 1 to carbon 2 c. Isomerase: aldose to ketose d. Can also catalyze conversion of other sugars e. Reversible reaction – can convert ketose to aldose 3. Phosphofructo-kinase-1 a. Phosphate comes from hydrolysis of ATP that’s converted to ADP b. Phosphorylates carbon 1 c. Irreversible reaction d. Need different enzyme for reverse reaction e. Regulation for glycolytic pathway occurs i. Senses level of energy (ATP) in cell ii. Either inhibited or activated based on energy levels f. Low concentration ATP in cell = enzyme remains active g. High concentration ATP in cell = enzyme inhibited i. Vmax same in both cases ii. Low ATP = Low Km iii. High ATP = High Km h. ATP inhibits the cell by increasing the Km, but not changing the Vmax (competitive inhibition) i. Enzyme regulated by other effectors 4. Aldolase a. Produce two 3 carbon molecules b. Breakdown between carbon 3 and carbon 4 c. Bis: two groups in different places d. Di: two group attached to each other e. One sugar is aldose 3 carbon f. One sugar is ketose 3 carbon g. Reversible reaction h. Starting point for the synthesis of lipids (dihydroxyacetone phosphate) 5. Triose Phospha
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