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Citric acid cycle (CAC). ط Citric acid cycle, Steps and enzymes ط Regulatory steps of CAC ط Energetic of CAC D4 231-239 , L2 467-469. Citric Acid Cycle (CAC). CAC is for complete oxidation of Glu (CO 2 +H 2 O) & production of further ATP in mitoch. matrix (mitosol)
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Citric acid cycle (CAC) ط Citric acid cycle, Steps and enzymes ط Regulatory steps of CAC ط Energetic of CAC D4 231-239 , L2 467-469
Citric Acid Cycle (CAC) CAC is for complete oxidation of Glu (CO2+H2O) & production of further ATP in mitoch. matrix (mitosol) fig6.18, ATP is generated: by high-energy phosphate bond (1 GTP) + by reducing equivalent (3 NADH, 1 FADH2) in the elect-trans-oxid phosph sequence(mitosol) fig6.19, OA (4C) + ACoA (2C) CS-ase (–CoA) "citroyl-SCoA as intermediate"C-ate (6C) A-tase "cis-Aconitate as intermediate" IsoC (6C) ICDH (+NADH/CO2) "oxalosuccinate as intermediate" α-KG (5C) α-KGDH (+NADH/CO2) SCoA (5C) SCoA S-tase (+GTP) "succinate phaphate as intermediate" S-ate (4C) SDH (+FADH2) F-ate (5C) F-aseM-ate (4C) MDH (+NADH/CO2) OA (4C) *Tricarboxylic Acid (TCA) cycle = Citric Acid Cycle (CAC) = Kreb's cycle
Regulation and characters of Citric acid cycle ط Inhibitors of CAC ط Amphibolic Nature of the cycle ط Anapleorotic reaction of CAC ط Reactions of CAC: stoichametry of CAC control of CAC ط Clinical correlation Pyruvate Dehydrogenase deficiency Fumarase deficiency D4 231-239 , L2 467-469
ACoA (2C) fate fig6.11, a) A (acetyl) + CoA (β-ME + PA + A, R) ACoA b) Acetate + CoA AK (–ATP) ACoA fig6.17, AA, FA, Pyr ACoA KB (only in liver mitosol) Cholesterol Citrate Carbon Source of Sterols & FA biosynthesis (cytosol) Source of Reducing Equivalent (cytosol) Other Metabolic Pathways Allosteric Regulation (cytosol) TCA cycle (mitosol)
CAC Regulation fig6.23, 1. OA + ACoA CS-ase(–) by acylCoA, SCoA, NADH, ATP (+) by ACoA, OACitarate * fig 6.20, Citrate ===> Carbon Source / Reducing Equivalent Source / Allosteric Regulator
CAC Regulation 2. Citrate A-tase (–) by MFC-ate (aninhibitor) (+) by Fe2+ IsoCitrate * Isocitrate continues in CAC
CAC Regulation 3. IsoCitrate ICDH(–) by ATP, NADH (+) by AMP, ADP, NAD+, Ca2+α-Ketoglutarate * α-KG ===> ammonia (urea) / AA metabolism (Glu = α-KG)
CAC Regulation fig, ICDH aPK (–) by IsoC, OA, Pyr, 3PG, PEP ICDH b ICDH bPP-tase (+) by IsoC, OA, Pyr, 3PG, PEP ICDH a
CAC Regulation 4. α-KG α-KGDH(–) by ATP, NADH, GTP, SCoA (+) by Ca2+ SCoA * fig 6.21, SCoA ===> PCoA / heme biosynthesis / KB utilization
CAC Regulation 5. Succinyl CoA SCoA S-taseSuccinate * Succinate continues in CAC
CAC Regulation 6. Succinate SDH(–) by OA, Malonate (an inhibitor) (+) by ATP, Pi, succinateFumarate * Fumarate ===> ammonia (urea) / Glu = α-KG
CAC Regulation 7. Fumarate Fumarase Malate * Malate ===> FA synth (Citrate) / Glu (OA)
CAC Regulation 8. Malate MDH(–) by NAD+ (+) by OAOA * OA ===> Pyr (PEP) / Asp (Pyrimidines)
fig, Anaplerotic reaction (CAC): Pyr Pyr C-lase (-CO2/ATP) OAPEP C-lase (CO2/Pi) PEP Pyr Malic Enz (NADPH) M-ate MDH (NADH) OA
Clinical Correlations Fumarase Deficiency: a) Deficiency in in both cytosolic (bld lymphocytes) and in mitosolic. b) High F-ate in urine & 1 more of C-ate, α-KG, S-ate, M-ate. c) Sever neurological impairment, encephalopathy & Dystonia (soon after birth). d) F-ase Deficiency is an autosomal recessive disorder (glu replaced by gln).