Enzymic Mechanisms in the Citric Acid Cycle

Ochoa, Severo

doi:10.1002/9780470122600.ch5

Cited by 18 publications

(3 citation statements)

References 212 publications

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“…Differential expression was found for 15 proteins, including citrate synthase (2.3.3.1) [44], malate dehydrogenase, cyto, mdh5, aconitate hydratase (4.2.1.3), phosphoenolpyruvate carboxykinase, isocitrate dehydrogenase (NAD+) (1.1.1.41) [45, 46], the succinyl-CoA synthetase beta subunit (6.2.1.4/6.2.1.5) [47, 48] and the pyruvate dehydrogenase E1 component alpha/beta subunit (1.2.4.1) [49, 50]. Succinyl-CoA ligase and phosphoenolpyruvate carboxykinase showed decreased levels and belong to class 1.…”

Section: Resultsmentioning

confidence: 99%

Proteomics analysis reveals a dynamic diurnal pattern of photosynthesis-related pathways in maize leaves

Feng

Wang

et al. 2017

PLoS ONE

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Plant leaves exhibit differentiated patterns of photosynthesis rates under diurnal light regulation. Maize leaves show a single-peak pattern without photoinhibition at midday when the light intensity is maximized. This mechanism contributes to highly efficient photosynthesis in maize leaves. To understand the molecular basis of this process, an isobaric tag for relative and absolute quantitation (iTRAQ)-based proteomics analysis was performed to reveal the dynamic pattern of proteins related to photosynthetic reactions. Steady, single-peak and double-peak protein expression patterns were discovered in maize leaves, and antenna proteins in these leaves displayed a steady pattern. In contrast, the photosystem, carbon fixation and citrate pathways were highly controlled by diurnal light intensity. Most enzymes in the limiting steps of these pathways were major sites of regulation. Thus, maize leaves optimize photosynthesis and carbon fixation outside of light harvesting to adapt to the changes in diurnal light intensity at the protein level.

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Section: Resultsmentioning

confidence: 99%

Proteomics analysis reveals a dynamic diurnal pattern of photosynthesis-related pathways in maize leaves

Feng

Wang

et al. 2017

PLoS ONE

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“…Citrate or 2-oxoglutaratedependent THNCoA reduction was most likely an artifact of the assay conditions, where 2-oxoglutarate served as indirect electron donor via oxidoreductase-mediated electron transfer, yielding NADH. Desulfobacterium strain N47 operates a modified citric acid cycle in which the ordinary 2-oxoglutarate dehydrogenase (38,39) is replaced by a 2-oxoglutarate:ferredoxin oxidoreductase (29). A similar oxidoreductase was also identified in strain NaphS2 (30).…”

Section: Discussionmentioning

confidence: 96%

The 5,6,7,8-Tetrahydro-2-Naphthoyl-Coenzyme A Reductase Reaction in the Anaerobic Degradation of Naphthalene and Identification of Downstream Metabolites

Weyrauch

Heker

Zaytsev

et al. 2020

Appl Environ Microbiol

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Anaerobic degradation of polycyclic aromatic hydrocarbons has been investigated mostly with naphthalene as a model compound. Naphthalene degradation by sulfate-reducing bacteria proceeds via carboxylation to 2-naphthoic acid, formation of a coenzyme A thioester, and subsequent reduction to 5,6,7,8-tetrahydro-2-naphthoyl-coenzyme A (THNCoA), which is further reduced to hexahydro-2-naphthoyl-CoA (HHNCoA) by tetrahydronaphthoyl-CoA reductase (THNCoA reductase), an enzyme similar to class I benzoyl-CoA reductases. When analyzing THNCoA reductase assays with crude cell extracts and NADH as electron donor via liquid chromatography-mass spectrometry (LC-MS), scanning for putative metabolites, we found that small amounts of the product of an HHNCoA hydratase were formed in the assays, but the downstream conversion by an NAD+-dependent β-hydroxyacyl-CoA dehydrogenase was prevented by the excess of NADH in those assays. Experiments with alternative electron donors indicated that 2-oxoglutarate can serve as an indirect electron donor for the THNCoA-reducing system via a 2-oxoglutarate:ferredoxin oxidoreductase. With 2-oxoglutarate as electron donor, THNCoA was completely converted and further metabolites resulting from subsequent β-oxidation-like reactions and hydrolytic ring cleavage were detected. These metabolites indicate a downstream pathway with water addition to HHNCoA and ring fission via a hydrolase acting on a β’-hydroxy-β-oxo-decahydro-2-naphthoyl-CoA intermediate. Formation of the downstream intermediate cis-2-carboxycyclohexylacetyl-CoA, which is the substrate for the previously described lower degradation pathway leading to the central metabolism, completes the anaerobic degradation pathway of naphthalene. IMPORTANCE Anaerobic degradation of polycyclic aromatic hydrocarbons is poorly investigated despite its significance in anoxic sediments. Using alternative electron donors for the 5,6,7,8-tetrahydro-2-naphthoyl-CoA reductase reaction, we observed intermediary metabolites of anaerobic naphthalene degradation via in vitro enzyme assays with cell extracts of anaerobic naphthalene degraders. The identified metabolites provide evidence that ring reduction terminates at the stage of hexahydro-2-naphthoyl-CoA and a sequence of β-oxidation-like degradation reactions starts with a hydratase acting on this intermediate. The final product of this reaction sequence was identified as cis-2-carboxycyclohexylacetyl-CoA, a compound for which a further downstream degradation pathway has recently been published (P. Weyrauch, A. V. Zaytsev, S. Stephan, L. Kocks, et al., Environ Microbiol 19:2819–2830, 2017, https://doi.org/10.1111/1462-2920.13806). Our study reveals the first ring-cleaving reaction in the anaerobic naphthalene degradation pathway. It closes the gap between the reduction of the first ring of 2-naphthoyl-CoA by 2-napthoyl-CoA reductase and the lower degradation pathway starting from cis-2-carboxycyclohexylacetyl-CoA, where the second ring cleavage takes place.

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“…Αυτή αποτελείται βασικως εκ τριών ενζύμων, τής πυροσταφυλικής άποκαρβοξυλάσης, τής λιποϊκής άκετυλοτρανσφεράσης και τής διϋδρολιποϊκής δεϋδρογενάσης. 41 , 153 Δια τήν εν λόγφ άντίδρασιν απαραίτητοι συνπαράγοντες, μεθ' ών σχηματίζονται ενδιάμεσα προϊόντα, είναι : Tò άκετυλ-CoA δρα ως συνπαράγων, ως άλλοστερικος ένεργοποιητής τοΰ ένζυμου, αυξάνοντας τήν δραστηριότητα του, διότι αυτή αυτή ή υπαρξις του όξαλοξεικοΰ οξέος είναι απαραίτητος δια τήν χρησιμοποίησιν του άκετυλ-CoA, προς σχηματισμόν του κιτρικού οξέος. Συνεπεία τούτου, όσον περισσότερον άκετυλ-CoA σχηματίζεται, τόσον περισσότερον όξαλοξεικόν απαιτείται, ό και επιτυγχάνεται κατόπιν της διεγερτικής δράσεως του πρώτου επί του ένζυμου.…”

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Επιδρασις Της Γλιβενκλαμιδης Επι Του Μεταβολισμου Των Υδατανθρακων Επι Σακχαρωδους Διαβητου Και Υπερθυρεοειδισμου

Αναπλιωτου-Βασιλοπουλου¹

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Περατωθείσης τής παρούσης εργασίας, ή οποία επραγματοποιήθη εις το Θυρεοειδικον Τμήμα της Θεραπευτικής Κλινικής τον Πανεπιστημίου 'Αθη νών, επιθυμώ όπως εκφράσω την ενγνωμοσύνην μου προς δλους εκείνους πλησίον τών οποίων εδιδάχθην εργαζομένη. Προς τον σεβαστόν μου Πανεπιστημιακον Διδάσκαλον καθηγητήν κ. Β. Μαλάμον εκφράζω την εύγνωμοσύνην μου, τόσον δια την ανάθεσιν τής παρούσης εργασίας δσον και δια την άμέριστον βοήθειάν του. Τον σεβαστόν μου καθηγητήν κοσμήτορα κ. Γ. Μερίκαν θερμώς ευχα ριστώ δια τήν εμπιστοσύνην δια τής οποίας με περιέβαλε κατά τήν εκτέλεσιν τής ερ^ασ/ας ταύτης. Προς τους ύφηγητάς και Διδασκάλους μου κ. κ. Σ. Μαρκέτον καί Α. Κούτραν, οι οποίοι υπεστήριζαν και καθωδήγησαν τήν δλην μου προσπάθειαν και τών οποίων ή μέριμνα δι εμε ύπήρξεν απεριόριστος, εκφράζω βαθυτάτην ενγνωμοσύνην και απείρους ευχαριστίας. Τέλος νποχρέωσιν θεωρώ δπως ευχαριστήσω θερμώς τον συνάδελφον κ. Α. Φαρμακιώτην δια τήν επιστημονικήν του βοήθειάν, ως και τον παρασκευαστήν κ. Ι. Παπαδόπονλον δια τάς πολλαπλώς παρασχεθείσας εις εμε υπη ρεσίας κατά τήν έκτέλεσιν τής παρούσης εργασίας.

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Enzymic Mechanisms in the Citric Acid Cycle

Cited by 18 publications

References 212 publications

Proteomics analysis reveals a dynamic diurnal pattern of photosynthesis-related pathways in maize leaves

Proteomics analysis reveals a dynamic diurnal pattern of photosynthesis-related pathways in maize leaves

The 5,6,7,8-Tetrahydro-2-Naphthoyl-Coenzyme A Reductase Reaction in the Anaerobic Degradation of Naphthalene and Identification of Downstream Metabolites

Επιδρασις Της Γλιβενκλαμιδης Επι Του Μεταβολισμου Των Υδατανθρακων Επι Σακχαρωδους Διαβητου Και Υπερθυρεοειδισμου

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