10-09-08 - oxaloacetate + 3NADPH + NH3 + 3ATP -> threonine...

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oxaloacetate + 3NADPH + NH 3 + 3ATP ---> threonine + 3NADP + + 3ADP + 3P i
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COO - H NH 3 + H 2 C H 2 C OPO 3 2- COO - H NH + H 2 C H 2 C OPO 3 2- N H + B H+ COO - NH + H C H 2 C OPO 3 2- N H + H B - NH + C H CH 2 N H + OH- H+ - NH + C H 3 N H + OH H B H+ - NH + C H 3 N H + H gamma lyase/beta synthase
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Threonine can be degraded in three ways (1) Threonine dehydrogenase pathway Threonine Dehydrogenase H C + H 3 N COO - O H CH 3 H B NAD+ H C + H 3 N COO - O CH 3
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H C COO - NH 3 + C OH S CH 3 CoA Must break C α -C β bond on an amino acid and stabilize a carbanion
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H C COO - NH 3 + C OH S CH 3 CoA N H + 2- O 3 PO O - C H O Schiff Base Formation N H + 2- O 3 PO O - C H H C COO - NH + C O S CH 3 CoA H B N H 2- O 3 PO O - C H H C COO - NH + H 3 C C O S CoA H A N H + 2- O 3 PO O - C H H C COO - NH + H Schiff Base Hydrolysis H C COO - NH 3 + C O CH 3 H S CoA B A N H + 2- O 3 PO O - C H O COO - C H H NH 3 + Glycine α-αμ ινο-β-κετοβυτψρατε 2-amino- α -ketobutyrate lyase
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What happens to the glycine? Glycine Cleavage System: trifunctional enzyme - OOC CH 2 NH 3 + N + 2- O 3 PO O - H C H O Schiff Base Formation N + 2- O 3 PO O - H C H C C NH + H H O O - CO 2 N 2- O 3 PO O - H C H C NH + H H S S E N + 2- O 3 PO O - H C H C NH + H H S E S - H A STEP1: decarboxylation of glycine
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N + 2- O 3 PO O - H C H O Schiff Base Hydrolysis N + 2- O 3 PO O - H C H C NH + H H S E SH N H N N R H H S E - CH 2 NH 2 B N H N N R H CH 2 H 2 N HS E HS B H A N H N N R CH 2 NH 3 N 5 ,N 10 -methylene tetrahydrofolate Tetrahydrofolate H A THF N 5 ,N 10 -methylene-THF STEP 2: formation of N 5 ,N 10 -methylene-THF
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S H H N + C O NH 2 R B E S S N C O NH 2 R NAD + NADH STEP 3: regeneration of catalytic site
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There is another pathway of glycine degradation From glycine cleavage system Combine the glycine cleavage system with a reverse of the serine hydroxymethyltransferase rxn N H N N R CH 2 N 5 ,N 10 -methylene-THF - OOC CH 2 NH 3 + N + 2- O 3 PO O - H C H Schiff Base Formation N + 2- O 3 PO O - H C H C C NH + H H O O - B N 2- O 3 PO O - H C H C C NH + H O O - H A
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N + 2- O 3 PO O - H C H C NH + H O - N H H N N R CH H O H B H A N + 2- O 3 PO O - H C H C C NH + H O O - HO N H H N HN R Schiff Base Hydrolysis THF H C CH 2 OH COO - NH 3 + N + 2- O 3 PO O - H C H O Serine So…2 glycine = 1 serine + NADH + NH 3
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If: Ser = pyruvate + NH 3 If: 2 Gly = serine + NADH + NH 3 Then: 2 Gly = 14 ATP, 1 Gly = 7 ATP Then: 2 Gly = pyruvate + NADH + 2 NH 3 If: Pyruvate = 4 NADH + GTP + FADH 2 Then: 2 Gly = 5 NADH + GTP + FADH 2 + 2 NH 3 If: NADH = 3 ATP GTP = ATP FADH 2 = 2 ATP NH 3 = -2 ATP
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If: glycine is degraded by glycine cleavage system you get 1 N 5 ,N 10 - methylene tetrahydrofolate, NH 3 and NADH If Acetyl-CoA = 3 NADH + GTP + FADH 2 So… Thr = Gly + Acetyl-CoA + NADH Then: Thr = N 5 ,N 10 -THF + NH 3 + 2 NADH + Acetyl-CoA Then: Thr = N 5 ,N 10 -THF + NH 3 + 5 NADH + GTP + FADH 2 If NADH = 3 ATP GTP = ATP FADH 2 = 2 ATP NH 3 = -2 ATP Then: Thr = N 5 ,N 10 -THF + 16 ATP
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If: 2 Thr are degraded to 2 Gly If: 1 Gly = N 5 ,N 10 - THF + 1 NH 3 + 1 NADH by glycine cleavage system Then: 2 Thr = 2 Gly + 2 NADH + 2 Acetyl-CoA And 1 Gly + N 5 ,N 10 -methylene tetrahydrofolate = serine by serine hydroxymethyltransferase If: Ser = pyruvate + NH 3 Then: 2 Thr = 1 NH 3 + 3 NADH + 2 Acetyl-CoA + serine Then: 2 Thr = 2 NH 3 + 3 NADH + 2 Acetyl-CoA + pyruvate If: Acetyl-CoA = 3 NADH + GTP + FADH 2
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This note was uploaded on 09/20/2011 for the course CHM 4034 taught by Professor Staff during the Summer '11 term at University of Florida.

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10-09-08 - oxaloacetate + 3NADPH + NH3 + 3ATP -> threonine...

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