scholarly journals Proton–Electron Transfer to the Active Site Is Essential for the Reaction Mechanism of Soluble Δ9-Desaturase

2020 ◽  
Vol 142 (23) ◽  
pp. 10412-10423 ◽  
Author(s):  
Daniel Bím ◽  
Jakub Chalupský ◽  
Martin Culka ◽  
Edward I. Solomon ◽  
Lubomír Rulíšek ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Reaction Mechanism ◽  
Active Site ◽  
Δ9 Desaturase

The crystal structure of human mitochondrial 3-ketoacyl-CoA thiolase (T1): insight into the reaction mechanism of its thiolase and thioesterase activities

2014 ◽  
Vol 70 (12) ◽  
pp. 3212-3225 ◽  
Author(s):  
Tiila-Riikka Kiema ◽  
Rajesh K. Harijan ◽  
Malgorzata Strozyk ◽  
Toshiyuki Fukao ◽  
Stefan E. H. Alexson ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Reaction Mechanism ◽  
Active Site ◽  
Quaternary Structure ◽  
Fatty Acyl ◽  
Physiological Importance ◽  
Loop Domain ◽  
Solution Studies ◽  
Hydrolysis Of ◽  
Insight Into

Crystal structures of human mitochondrial 3-ketoacyl-CoA thiolase (hT1) in the apo form and in complex with CoA have been determined at 2.0 Å resolution. The structures confirm the tetrameric quaternary structure of this degradative thiolase. The active site is surprisingly similar to the active site of theZoogloea ramigerabiosynthetic tetrameric thiolase (PDB entries 1dm3 and 1m1o) and different from the active site of the peroxisomal dimeric degradative thiolase (PDB entries 1afw and 2iik). A cavity analysis suggests a mode of binding for the fatty-acyl tail in a tunnel lined by the Nβ2–Nα2 loop of the adjacent subunit and the Lα1 helix of the loop domain. Soaking of the apo hT1 crystals with octanoyl-CoA resulted in a crystal structure in complex with CoA owing to the intrinsic acyl-CoA thioesterase activity of hT1. Solution studies confirm that hT1 has low acyl-CoA thioesterase activity for fatty acyl-CoA substrates. The fastest rate is observed for the hydrolysis of butyryl-CoA. It is also shown that T1 has significant biosynthetic thiolase activity, which is predicted to be of physiological importance.

scholarly journals One-megadalton metalloenzyme complex inGeobacter metallireducensinvolved in benzene ring reduction beyond the biological redox window

2019 ◽  
Vol 116 (6) ◽  
pp. 2259-2264 ◽  
Author(s):  
Simona G. Huwiler ◽  
Claudia Löffler ◽  
Sebastian E. L. Anselmann ◽  
Hans-Joachim Stärk ◽  
Martin von Bergen ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Benzene Ring ◽  
Active Site ◽  
Anaerobic Bacterium ◽  
Class Ii ◽  
High Molecular Mass ◽  
Redox Potentials ◽  
Geobacter Metallireducens ◽  
Redox Couples ◽  
Biological Electron Transfer

Reversible biological electron transfer usually occurs between redox couples at standard redox potentials ranging from +0.8 to −0.5 V. Dearomatizing benzoyl-CoA reductases (BCRs), key enzymes of the globally relevant microbial degradation of aromatic compounds at anoxic sites, catalyze a biological Birch reduction beyond the negative limit of this redox window. The structurally characterized BamBC subunits of class II BCRs accomplish benzene ring reduction at an active-site tungsten cofactor; however, the mechanism and components involved in the energetic coupling of endergonic benzene ring reduction have remained hypothetical. We present a 1-MDa, membrane-associated, Bam[(BC)2DEFGHI]2complex from the anaerobic bacteriumGeobacter metallireducensharboring 4 tungsten, 4 zinc, 2 selenocysteines, 6 FAD, and >50 FeS cofactors. The results suggest that class II BCRs catalyze electron transfer to the aromatic ring, yielding a cyclic 1,5-dienoyl-CoA via two flavin-based electron bifurcation events. This work expands our knowledge of energetic couplings in biology by high-molecular-mass electron bifurcating machineries.

scholarly journals Reaction Mechanism of the ε Subunit ofE. coliDNA Polymerase III: Insights into Active Site Metal Coordination and Catalytically Significant Residues

2009 ◽  
Vol 131 (4) ◽  
pp. 1550-1556 ◽  
Author(s):  
G. Andrés Cisneros ◽  
Lalith Perera ◽  
Roel M. Schaaper ◽  
Lars C. Pedersen ◽  
Robert E. London ◽  
...  
Keyword(s):  
Reaction Mechanism ◽  
Active Site ◽  
Metal Coordination ◽  
Polymerase Iii

scholarly journals Structural evidence for the covalent modification of FabH by 4,5-dichloro-1,2-dithiol-3-one (HR45)

2017 ◽  
Vol 15 (30) ◽  
pp. 6310-6313 ◽  
Author(s):  
Alexander G. Ekström ◽  
Van Kelly ◽  
Jon Marles-Wright ◽  
Scott L. Cockroft ◽  
Dominic J. Campopiano
Keyword(s):  
Mass Spectrometry ◽  
Reaction Mechanism ◽  
Active Site ◽  
Covalent Modification ◽  
Elimination Reaction ◽  
Covalent Adduct ◽  
Michael Type Addition

Mass spectrometry and modelling shows the antimicrobial inhibitor 4,5-dichloro-1,2-dithiol-3-one (HR45) acts by forming a covalent adduct with the target β-ketoacyl-ACP synthase III (FabH). The 5-chloro substituent directs attack of the essential active site thiol (C112) via a Michael type addition elimination reaction mechanism.

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