Lecture_20_4-8-10-PDF_41577

Lecture_20_4-8-10-PDF_41577 - Amino Acid Metabolism (Lec...

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Amino Acid Metabolism (Lec 18-21) 4. Breakdown of Amino Acids 5. Amino acid biosynthesis 6. Other products of amino acid metabolism 7. Nitrogen fixation Lec 20 Lec 21
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The carbon atoms of degraded amino acids emerge as major metabolic intermediates. Degradation of the 20 amino acids funnel into 7 metabolic intermediates Breakdown of amino acids 1. Acetyl–CoA 2. Acetoacetate 3. Pyruvate 4. α-Ketoglutarate 5. Succinyl–CoA 6. Fumarate 7. Oxaoloacetate
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Breakdown of amino acids: overview Glucogenic Glucose precursors Ketogenic Fatty acids Ketone bodies precursoes
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Both Isoleucine (I) Phenylalanine (F) Tryptophan (W) Tyrosine (Y) Ketogenic Leucine (L) Lysine (K) Glucogenic Serine (S) Threonine (T) Aspartic acid (D) Glutamic acid (E) Asparagine (N) Glutamine (Q) Glycine (G) Alanine (A) Valine (V) Proline (P) Histidine (H) Arginine (R) Methionine (M) Cysteine (C)
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Gluconeogenesis is the process whereby precursors such as lactate , pyruvate , glycerol , and amino acids are converted to glucose Gluconeogenesis Lec-4 Fasting requires all the glucose to be synthesized from these non-carbohydrate precursors When dietary sources of glucose are not available and when the liver has exhausted its supply of glycogen, glucose is synthesized from noncarbohydrate precursours When?
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Oxidative fuel metabolism Lec-4
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Degradation of amino acids to one of seven common metabolic intermediates 5 main entry points to the TCA 1 1. Pyruvate 2. Oxaloacetate 2 3. a -ketoglutarate 3 4. Succinyl-CoA 4 5. Fumarate 5
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Pyruvate entry point ( Reactions 1-7 ) ( ) Both (Gluco/Keto) isoleucine phenylalanine tryptophan tyrosine Pyruvate entry point
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Alanine becomes pyruvate as the amino group is transferred to a -KG Fig. 21-14 ( Reaction 1 ), p748 alanine a -ketoglutarate pyruvate glutamate Aminotransferase (Transaminase) COO CH 2 CH 2 C COO O CH 3 HC COO NH 3 + COO CH 2 CH 2 HC COO NH 3 + CH 3 C COO O + + Pyruvate entry point
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Fig. 21-14 ( Reaction 2 ), p748 Serine is converted to pyruvate through dehydration by serine dehydratase Pyruvate entry point
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Deamination occurs through a PLP intermediate in the serine dehydratase reaction COO - H 2 C C H NH 3 + H O Serine PLP Fig. 21-15 ( Reaction 2 ), p749 Pyruvate entry point
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Methylene group ( CH 2 ) is obtained from a second glycine by the glycine cleavage system Fig. 21-14 ( Reaction 3 ), p748 Pyruvate entry point
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Glycine is converted to serine by the enzyme serine hydroxymethyltransferase (PLP-containing enzyme) Fig. 21-14 ( Reaction 4 ), p749 Pyruvate entry point
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Uses N 5 ,N 10 -methylene tetrahydrofolate to carry the methylene group. The enzyme (glycine cleavage system) is multi subunit that resembles pyruvate dehydrogenase . Defects in this enzyme leads to nonketotic hyperglycemia- mental retardation and large amounts of glycine Tetrahydrofolate (THF) Fig. 21-14 ( Reactions 3 & 4 ), p749 Pyruvate entry point
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Cofactors involved in the degradation of amino acids 1. PLP: mediate the catalytic breakdown of the C a -C b bond in thr to generate gly and acetaldehyde 2. THF : serves as a one-carbon carrier in several reactions 3. Biopterin: involved in oxidation of phe to tyr 4. SAM: a potent methylating reagent in several reactions
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One carbon metabolism THF (tetrahydrofolate) can transfer one carbon groups in many oxidation states
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This note was uploaded on 09/15/2010 for the course BCHS 3305 taught by Professor Fujita during the Spring '10 term at University of Houston.

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Lecture_20_4-8-10-PDF_41577 - Amino Acid Metabolism (Lec...

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