Proton uptake accompanies formation of the ternary complex of citrate synthase, oxaloacetate, and the transition-state analog inhibitor, carboxymethyl-CoA. Evidence that a neutral enol is the activated form of acetyl-CoA in the citrate synthase reaction

Biochemistry ◽  
1992 ◽  
Vol 31 (34) ◽  
pp. 7899-7907 ◽  
Author(s):  
Linda C. Kurz ◽  
Saurabh Shah ◽  
Brian R. Crane ◽  
Lynda J. Donald ◽  
Harry W. Duckworth ◽  
...  
Keyword(s):  
Transition State ◽  
Ternary Complex ◽  
Citrate Synthase ◽  
Acetyl Coa ◽  
Transition State Analog ◽  
Proton Uptake

Catalytic strategy of citrate synthase: effects of amino acid changes in the acetyl-CoA binding site on transition-state analog inhibitor complexes

Biochemistry ◽  
1992 ◽  
Vol 31 (34) ◽  
pp. 7908-7914 ◽  
Author(s):  
Linda C. Kurz ◽  
George R. Drysdale ◽  
Marian C. Riley ◽  
Claudia T. Evans ◽  
Paul A. Srere
Keyword(s):  
Amino Acid ◽  
Transition State ◽  
Binding Site ◽  
Citrate Synthase ◽  
Acetyl Coa ◽  
Transition State Analog

scholarly journals Analysis of the mechanism of chloramphenicol acetyltransferase by steady-state kinetics. Evidence for a ternary-complex mechanism

1984 ◽  
Vol 223 (1) ◽  
pp. 211-220 ◽  
Author(s):  
C Kleanthous ◽  
W V Shaw
Keyword(s):  
Steady State ◽  
Ternary Complex ◽  
Citrate Synthase ◽  
Dissociation Constants ◽  
Antibiotic Use ◽  
Chloramphenicol Acetyltransferase ◽  
Acetyl Coa ◽  
Kinetic Measurements ◽  
Chloramphenicol Resistance ◽  
Rapid Equilibrium

The mechanism of the enzymic reaction responsible for chloramphenicol resistance in bacteria was examined by steady-state kinetic methods. The forward reaction catalysed by chloramphenicol acetyltransferase leads to inactivation of the antibiotic. Use of alternative acyl donors and acceptors, as well as the natural substrates, has yielded data that favour the view that the reaction proceeds to the formation of a ternary complex by a rapid-equilibrium mechanism wherein the addition of substrates may be random but a preference for acetyl-CoA as the leading substrate can be detected. Chloramphenicol and acetyl-CoA bind independently, but the correlation between directly determined and kinetically derived dissociation constants is imperfect because of an unreliable slope term in the rate equation. The reverse reaction, yielding acetyl-CoA and chloramphenicol, was studied in a coupled assay involving citrate synthase and malate dehydrogenase, and is best described by a rapid-equilibrium mechanism with random addition of substrates. The directly determined dissociation constant for CoA is in agreement with that derived from kinetic measurements under the assumption of an independent-sites model.

Acetyl-CoA is produced by the citrate synthase homology module of ATP-citrate lyase

2021 ◽  
Author(s):  
Kenneth Verstraete ◽  
Koen H. G. Verschueren ◽  
Ann Dansercoer ◽  
Savvas N. Savvides
Keyword(s):  
Citrate Synthase ◽  
Atp Citrate Lyase ◽  
Acetyl Coa ◽  
Citrate Lyase ◽  
Homology Module

Renin inhibitors. Synthesis of transition-state analog inhibitors containing phosphorus acid derivatives at the scissile bond

1989 ◽  
Vol 32 (7) ◽  
pp. 1652-1661 ◽  
Author(s):  
Mark C. Allen ◽  
Walter Fuhrer ◽  
Brian Tuck ◽  
Roy Wade ◽  
Jeanette M. Wood
Keyword(s):  
Transition State ◽  
Phosphorus Acid ◽  
Transition State Analog ◽  
Renin Inhibitors ◽  
Scissile Bond

scholarly journals Association of the malate dehydrogenase-citrate synthase metabolon is modulated by intermediates of the Krebs tricarboxylic acid cycle

2021 ◽  
Author(s):  
Joy Omini ◽  
Izabela Wojciechowska ◽  
Aleksandra Skirycz ◽  
Hideaki Moriyama ◽  
Toshihiro Obata
Keyword(s):  
Malate Dehydrogenase ◽  
Metabolic Flux ◽  
Citrate Synthase ◽  
Tricarboxylic Acid Cycle ◽  
Feedback Regulation ◽  
Dynamic Structure ◽  
Tca Cycle ◽  
Tricarboxylic Acid ◽  
Enzyme Complex ◽  
Acetyl Coa

Mitochondrial malate dehydrogenase (MDH)-citrate synthase (CS) multi-enzyme complex is a part of the Krebs tricarboxylic acid (TCA) cycle 'metabolon' which is enzyme machinery catalyzing sequential reactions without diffusion of reaction intermediates into a bulk matrix. This complex is assumed to be a dynamic structure involved in the regulation of the cycle by enhancing metabolic flux. Microscale Thermophoresis analysis of the porcine heart MDH-CS complex revealed that substrates of the MDH and CS reactions, NAD+ and acetyl-CoA, enhance complex association while products of the reactions, NADH and citrate, weaken the affinity of the complex. Oxaloacetate enhanced the interaction only when it was presented together with acetyl-CoA. Structural modeling using published CS structures suggested that the binding of these substrates can stabilize the closed format of CS which favors the MDH-CS association. Two other TCA cycle intermediates, ATP, and low pH also enhanced the association of the complex. These results suggest that dynamic formation of the MDH-CS multi-enzyme complex is modulated by metabolic factors responding to respiratory metabolism, and it may function in the feedback regulation of the cycle and adjacent metabolic pathways.

scholarly journals A crystallographic study of the Toho-1 β-lactamase acylation mechanism

2014 ◽  
Vol 70 (a1) ◽  
pp. C1207-C1207
Author(s):  
Leighton Coates
Keyword(s):  
Hydrogen Bonding ◽  
Transition State ◽  
Active Site ◽  
Catalytic Mechanism ◽  
Substrate Binding ◽  
Ligand Complex ◽  
Transition State Analog ◽  
Hydrogen Bonding Interactions ◽  
Active Site Region ◽  
Neutron Crystallography

β-lactam antibiotics have been used effectively over several decades against many types of highly virulent bacteria. The predominant cause of resistance to these antibiotics in Gram-negative bacterial pathogens is the production of serine β-lactamase enzymes. A key aspect of the class A serine β-lactamase mechanism that remains unresolved and controversial is the identity of the residue acting as the catalytic base during the acylation reaction. Multiple mechanisms have been proposed for the formation of the acyl-enzyme intermediate that are predicated on understanding the protonation states and hydrogen-bonding interactions among the important residues involved in substrate binding and catalysis of these enzymes. For resolving a controversy of this nature surrounding the catalytic mechanism, neutron crystallography is a powerful complement to X-ray crystallography that can explicitly determine the location of deuterium atoms in proteins, thereby directly revealing the hydrogen-bonding interactions of important amino acid residues. Neutron crystallography was used to unambiguously reveal the ground-state active site protonation states and the resulting hydrogen-bonding network in two ligand-free Toho-1 β-lactamase mutants which provided remarkably clear pictures of the active site region prior to substrate binding and subsequent acylation [1,2] and an acylation transition-state analog, benzothiophene-2-boronic acid (BZB), which was also isotopically enriched with 11B. The neutron structure revealed the locations of all deuterium atoms in the active site region and clearly indicated that Glu166 is protonated in the BZB transition-state analog complex. As a result, the complete hydrogen-bonding pathway throughout the active site region could then deduced for this protein-ligand complex that mimics the acylation tetrahedral intermediate [3].

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