lecture 4

lecture 4 - Bis 103 - 04 - Anaplerotic Reactions...

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Unformatted text preview: Bis 103 - 04 - Anaplerotic Reactions Anaplerotic reactions to replenish the TCA cycle Pyruvate carboxylase - Biotin PEP carboxykinase PEP carboxylase Malic enzyme Glyoxylate cycle isocitrate lyase malate synthase succinate produced for TCA cycle Plants and microorganisms and glyoxylate cycle Acetate as sole source of carbon Regulation of isocitrate dehydrogenase and isocitrate lyase Finish TCA lecture COOH C=O CH 2 COOH COOH C=O CH 2 COOH CH 2 COOH C-H CH 2 COOH NH 2- COOH C-H CH 2 COOH CH 2 NH 2- COOH C=O CH 3 COOH C-H CH 3 NH 2- BIS 103 - 03 -keto acids and amino acids TCA intermediates such as oxaloacetate and -ketoglutarate can be drawn away from the TCA cycle to make amino acids. When this happens, the TCA cycle would stop unless anaplerotic reactIons occurred. Anaplerotic means to Fll up and anaplerotic reactions, which will be discussed In the this lecture, supply TCA intermediates that allow the cycle to continue when TCA intermediates are removed for other purposes. You should know the structures of these common -keto acids and their cognate amino acids. pyruvate alanine oxaloacetate aspartate -ketoglutarate glutamate BIS 103 - #4 - Anaplerotic reactions What are anaplerotic reactions? They are replenishing reactions for metabolic cycles. The following 5 reactions are anaplerotic reactions for the citric acid cycle when TCA cycle intermediates are removed for biosynthetic purposes. pyruvate + HCO 3- + ATP oxaloacetate + ADP + Pi See Page 23 biotin (+)acetyl-CoA 1. Pyruvate carboxylase- found in liver and kidney The pyruvate carboxylase reaction is the most important anaplerotic reaction carried out in the liver and kidney. ATP furnishes energy; biotin is the co-factor; absolute requirement BIS 103 - #4 - Anaplerotic reactions What are anaplerotic reactions? They are replenishing reactions for metabolic cycles. The following 5 reactions are anaplerotic reactions for the citric acid cycle when TCA cycle intermediates are removed for biosynthetic purposes. pyruvate + HCO 3- + ATP oxaloacetate + ADP + Pi See Page 23 biotin (+)acetyl-CoA 1. Pyruvate carboxylase- found in liver and kidney The pyruvate carboxylase reaction is the most important anaplerotic reaction carried out in the liver and kidney. ATP furnishes energy; biotin is the co-factor; absolute requirement for acetyl-CoA. phosphoenolpyruvate + CO 2 +GDP oxaloacetate + GTP (PEP) OAA) This enzyme is important for gluconeogenesis which will be discussed later in the quarter. This reaction is reversible under intracellular conditions. 2. PEP carboxykinase - found in heart, skeletal muscle phosphoenolpyruvate + HCO 3- oxaloacetate + Pi (PEP) (OAA) This is an irreversible reaction. The enzyme is not found in animals....
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lecture 4 - Bis 103 - 04 - Anaplerotic Reactions...

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