Cyclus acidi citrici

Cyclus acidi citrici vel cylcus acidorum triclyclicorum vel tricarboxylici acidi cyclus vel cyclus Krebs est iter metabolicum intracellulare et iter paenultimum in mitochondriis, ante phosphorylationem oxydativam enim, energiam cellularem (ATP) generantem.

Cyclus ex pyruvato et, non exigue, aqua generat duo substantias, electrona e- in proximum iter portantes: NADH+H+ et FAD(2H).

Hic cyclus anno 1937 ab Iohanne Adolpho Krebs primo descriptus est; nimirum Krebs anno 1953 praemium Nobelianum physiologiae et medicinae addictum estDe Iohanne Adolpho Krebs in situ praemio Nobeliano medicinae dicato . Hac de causa cyclus non raro "cyclus Krebs" appellatur. Praeterea nomen "cycli acidorum tricyclicorum" de tribus acidis tricyclicis intra cyclum Krebs (citrato, aconitato, isocitrato) partibus cursus cycli sumitur; denique nomen "cycli acidi citrici" de molecula acidi citrici, non electrice onerati, derivatur, quamquam citratum forma electrice onerata partem cycli ipsius capit.

 Cursus 
Aequatio generalis cycli Krebs:
Acetylo-CoA + 3 NAD+ + FAD + GDP + Pi+ 2 H2O → CoA + 3 NADH + 3 H+ + FAD(2H) + GTP + 2 CO2
Nota cycli Krebs ope, nec oxygenium consumatur, nec ATP generetur, sed generentur GTP et CO2. Oxygenium quidem, ut ATP, demum in itinere proximo, phosphorylatione oxydativa, momenta maxima habebit.

 Condiciones 
 Substrata pyruvatum generantia
 Aqua (cyclo 2 moleculae)
 Mitochondria sana

 Gradus cycli acidi citrici 
 Reactio biochemica 0/10 (Citrati synthasis): Oxaloacetatum + Acetylo-CoA + H2O → Citratum + CoA-SH
 Reactio biochemica 1 (Aconitasis): Citratum + CoA-SH → cis-Aconitatum + H2O
 Reactio biochemica 2 (Aconitasis): cis-Aconitatum + H2O → Isocitratum
 Reactio biochemica 3 (Isocitrati dehydrogenasis): Isocitratum + NAD+ → Oxalosuccinatum + NADH + H+
 Reactio biochemica 4 (Isocitrati dehydrogenasis): Oxalosuccinatum → α-Ketoglutaratum + CO2
 Reactio biochemica 5 (α-Ketoglutarate dehydrogenasis): α-Ketoglutaratum + NAD+ + CoA-SH → Succinylo-CoA + NADH + H+ + CO2
 Reactio biochemica 6 (Succinylo-CoA synthetasis): Succinylo-CoA + GDP + Pi → Succinatum + CoA-SH + GTP
 Reactio biochemica 7 (Succinati dehydrogenasis): Succinatum + Ubiquinonum (Q) → Fumaratum + Ubiquilonum (QH2)
 Reactio biochemica 8 (Fumarasis): Fumaratum + H2O → L-Malatum
 Reactio biochemica 9 (Malati dehydrogenasis) L-Malatum + NAD+ → Oxaloacetatum + NADH + H+
 Reactio biochemica 10/0 (Citrati synthasis): Oxaloacetatum + Acetylo-CoA + H2O → Citratum + CoA-SH

 Eventus 
 Electrona (cyclo 3 moleculae NADH+H+, 1 molecula FAD(2H))
 GTP (cyclo 1 molecula)
 CO2 (cyclo 2 moleculae, aeris exspirati)
 Succinylo coenzymum A in parte in synthesem porphyrini defertur.

 Notae 

 Plura legere si cupis 
Jean-Jacques Brière 1, Judith Favier, Anne-Paule Gimenez-Roqueplo, Pierre Rustin. "Tricarboxylic acid cycle dysfunction as a cause of human diseases and tumor formation", Review Am J Physiol Cell Physiol, 2006ː C1114-C1120
Gray, L.R., Tompkins, S.C. & Taylor, E.B. "Regulation of pyruvate metabolism and human disease". Cell. Mol. Life Sci., 2014ː 2577–2604 
Oliver E. Owen, Satish C. Kalhan, Richard W. Hanson. "The key role of Anaplerosis and Cataplerosis for Citric Acid Cycle Function", The Journal of biological Chemistry, 2002ː 30409-30412
Mulchand S. Patel, Natalia S. Nemeria, William Furey and Frank Jordan. "The Pyruvate Dehydrogenase Complexes: Structure-based Function and Regulation", Journal of biological Chemistry, 2014: 16615–16623

 Acidum fumaricum
 Energia
 Mitochondrium

 Nexus externi 
 Khan academy de cycli acidi citrici. 
 Alii cursus cycli Krebs. 

Categoria:Biochemia
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Categoria:Itinera metabolica