1115-65-7Relevant academic research and scientific papers
Steady-state substrate specificity and O2-coupling efficiency of mouse cysteine dioxygenase
Li, Wei,Pierce, Brad S.
, p. 49 - 56 (2015)
Cysteine dioxygenase (CDO) is a non-heme mononuclear iron enzyme that catalyzes the oxygen-dependent oxidation of l-cysteine (Cys) to produce l-cysteine sulfinic acid (CSA). Sequence alignment of mammalian CDO with recently discovered thiol dioxygenase enzymes suggests that the mononuclear iron site within all enzymes in this class share a common 3-His first coordination sphere. This implies a similar mechanistic paradigm among thiol dioxygenase enzymes. Although steady-state studies were first reported for mammalian CDO over 45 years ago, detailed analysis of the specificity for alternative thiol-bearing substrates and their oxidative coupling efficiencies have not been reported for this enzyme. Assuming a similar mechanistic theme among this class of enzymes, characterization of the CDO substrate specificity may provide valuable insight into substrate-active site intermolecular during thiol oxidation. In this work, the substrate-specificity for wild-type Mus musculus CDO was investigated using NMR spectroscopy and LC-MS for a variety of thiol-bearing substrates. Tandem mass spectrometry was used to confirm dioxygenase activity for each non-native substrate investigated. Steady-state Michaelis-Menten parameters for sulfinic acid product formation and O2-consumption were compared to establish the coupling efficiency for each reaction. In light of these results, the minimal substrate requirements for CDO catalysis and O2-activation are discussed.
Bioinformatic and biochemical characterizations of C-S bond formation and cleavage enzymes in the fungus neurospora crassa ergothioneine biosynthetic pathway
Hu, Wen,Song, Heng,Her, Ampon Sae,Bak, Daniel W.,Naowarojna, Nathchar,Elliott, Sean J.,Qin, Li,Chen, Xiaoping,Liu, Pinghua
, p. 5382 - 5385 (2014)
Ergothioneine is a histidine thiol derivative. Its mycobacterial biosynthetic pathway has five steps (EgtA-E catalysis) with two novel reactions: a mononuclear nonheme iron enzyme (EgtB) catalyzed oxidative C-S bond formation and a PLP-mediated C-S lyase (EgtE) reaction. Our bioinformatic and biochemical analyses indicate that the fungus Neurospora crassa has a more concise ergothioneine biosynthetic pathway because its nonheme iron enzyme, Egt1, makes use of cysteine instead of γ-Glu-Cys as the substrate. Such a change of substrate preference eliminates the competition between ergothioneine and glutathione biosyntheses. In addition, we have identi fied the N. crassa C-S lyase (NCU11365) and reconstituted its activity in vitro, which makes the future ergothioneine production through metabolic engineering feasible. (Chemical Equation Presented).
Reduction mechanism of a coordinated superoxide by thiols in acidic media
Mishra, Ritu,Mukhopadhyay, Subrata,Banerjee, Rupendranath
, p. 2692 - 2696 (2010)
In weakly acidic media ([H+], 0.01-0.06 M), 2-mercaptoethanol (mercap, RSH), thioglycolic acid (tga, R′SH) and l-cysteine (cys, R′′SH) reduce the superoxo ligand of the complex ion, {μ-amido-μ-superoxo-bis[tetraamminecobalt(iii)]}4+ (1) to its corresponding hydroperoxo complex, {μ-amido-μ-hydroperoxo- bis[tetraamminecobalt(iii)]}3+ (2). During this act, RSH and R′SH are quantitatively oxidized to their respective disulfides. However, cysteine (R′′SH) is converted to a mixture of ～80% of the disulfide, cystine and ～20% to cystine sulfinic acid. Cystine itself is not a source of the sulfinic acid. Dissolved copper, even at the impurity level, dramatically catalyzes the reaction such that the direct reactions are inaccessible. Nevertheless, the catalyzed path can be masked completely with 0.20 mM dipicolinic acid and it can be determined for the first time that, the direct reactions are first-order in [1], in [total thiol] and in basicity. Rate decreases linearly with increasing mol% of D2O in the solvent. H-atom (H+ + e) transfer from thiols to superoxide in 1 seems logical for the conversion of 1 to 2. The Royal Society of Chemistry 2010.
Shifting redox states of the iron center partitions CDO between crosslink formation or cysteine oxidation
Njeri, Catherine W.,Ellis, Holly R.
, p. 61 - 69 (2014)
Cysteine dioxygenase (CDO) is a mononuclear iron-dependent enzyme that catalyzes the oxidation of l-cysteine to l-cysteine sulfinic acid. The mammalian CDO enzymes contain a thioether crosslink between Cys93 and Tyr157, and purified recombinant CDO exists as a mixture of the crosslinked and non crosslinked isoforms. The current study presents a method of expressing homogenously non crosslinked CDO using a cell permeative metal chelator in order to provide a comprehensive investigation of the non crosslinked and crosslinked isoforms. Electron paramagnetic resonance analysis of purified non crosslinked CDO revealed that the iron was in the EPR silent Fe(II) form. Activity of non crosslinked CDO monitoring dioxygen utilization showed a distinct lag phase, which correlated with crosslink formation. Generation of homogenously crosslinked CDO resulted in an ～5-fold higher kcat/Km value compared to the enzyme with a heterogenous mixture of crosslinked and non crosslinked CDO isoforms. EPR analysis of homogenously crosslinked CDO revealed that this isoform exists in the Fe(III) form. These studies present a new perspective on the redox properties of the active site iron and demonstrate that a redox switch commits CDO towards either formation of the Cys93-Tyr157 crosslink or oxidation of the cysteine substrate.
Use of a Tyrosine Analogue to Modulate the Two Activities of a Nonheme Iron Enzyme OvoA in Ovothiol Biosynthesis, Cysteine Oxidation versus Oxidative C-S Bond Formation
Chen, Li,Naowarojna, Nathchar,Song, Heng,Wang, Shu,Wang, Jiangyun,Deng, Zixin,Zhao, Changming,Liu, Pinghua
, p. 4604 - 4612 (2018)
Ovothiol is a histidine thiol derivative. The biosynthesis of ovothiol involves an extremely efficient trans-sulfuration strategy. The nonheme iron enzyme OvoA catalyzed oxidative coupling between cysteine and histidine is one of the key steps. Besides catalyzing the oxidative coupling between cysteine and histidine, OvoA also catalyzes the oxidation of cysteine to cysteine sulfinic acid (cysteine dioxygenase activity). Thus far, very little mechanistic information is available for OvoA-catalysis. In this report, we measured the kinetic isotope effect (KIE) in OvoA-catalysis using the isotopically sensitive branching method. In addition, by replacing an active site tyrosine (Tyr417) with 2-amino-3-(4-hydroxy-3-(methylthio)phenyl)propanoic acid (MtTyr) through the amber suppressor mediated unnatural amino acid incorporation method, the two OvoA activities (oxidative coupling between cysteine and histidine, and cysteine dioxygenase activity) can be modulated. These results suggest that the two OvoA activities branch out from a common intermediate and that the active site tyrosine residue plays some key roles in controlling the partitioning between these two pathways.
Substrate and pH-Dependent Kinetic Profile of 3-Mercaptopropionate Dioxygenase from Pseudomonas aeruginosa
Fellner, Matthias,Aloi, Sekotilani,Tchesnokov, Egor P.,Wilbanks, Sigurd M.,Jameson, Guy N.L.
, p. 1362 - 1371 (2016)
Thiol dioxygenases catalyze the synthesis of sulfinic acids in a range of organisms from bacteria to mammals. A thiol dioxygenase from the bacterium Pseudomonas aeruginosa oxidizes both 3-mercaptopropionic acid and cysteine, with a ～70 fold preference for 3-mercaptopropionic acid over all pHs. This substrate reactivity is widened compared to other thiol dioxygenases and was exploited in this investigation of the residues important for activity. A simple model incorporating two protonation events was used to fit profiles of the Michaelis-Menten parameters determined at different pH values for both substrates. The pKs determined using plots of kcat/Km differ at low pH, but not in a way easily attributable to protonation of the substrate alone and share a common value at higher pH. Plots of kcat versus pH are also quite different at low pH showing the monoprotonated ES complexes with 3-mercaptopropionic acid and cysteine have different pKs. At higher pH, kcat decreases sigmoidally with a similar pK regardless of substrate. Loss of reactivity at high pH is attributed to deprotonation of tyrosine 159 and its influence on dioxygen binding. A mechanism is proposed by which deprotonation of tyrosine 159 both blocks oxygen binding and concomitantly promotes cystine formation. Finally, the role of tyrosine 159 was further probed by production of a G95C variant that is able to form a cysteine-tyrosine crosslink homologous to that found in mammalian cysteine dioxygenases. Activity of this variant is severely impaired. Crystallography shows that when un-crosslinked, the cysteine thiol excludes tyrosine 159 from its native position, while kinetic analysis shows that the thioether bond impairs reactivity of the crosslinked form.
Chemical properties of N-chlorotaurine sodium, a key compound in the human defence system
Gottardi, Waldemar,Nagl, Markus
, p. 411 - 421 (2007/10/03)
N-Chlorotaurine (NCT) is known to play an important role in the human defence system. The already proved utility of the sodium salt as a disinfectant in human medicine suggested a thorough investigation of its chemical properties. Chlorine transfer to N-H groups (transhalogenation) and oxidation of thio and aromatic compounds represent its main reactions. Auto-chlorination causes disproportionation forming N,N-dichlorotaurine (NDCT) with Kd = [NDCT][taurine]/fa[NCT]2 aH+ = (4.5 ± 0.8) times; 106, while the reaction with ammonium releasing NH2Cl is characterised by KNHC2 = [NH2Cl][taurine]/[NCT][NH4+] fa2 = 0.02 ± 0.004. The verified unique stability and low-level reactivity of NCT are considered essential for its function in the mammalian defence system and its practical applicability, which manifests itself in an optimal compromise between microbicidal activity and toxicity.
Kinetics and mechanism of the reactions of superoxochromium(III) ion with biological thiols
Perez-Benito, Joaquin F.,Arias, Conchita
, p. 5837 - 5845 (2007/10/03)
The kinetics of the oxidation of three biological thiols (L-cysteine, glutathione, and DL-penicillamine) to their sulfinic and sulfonic acid derivatives by CrOO2+ in aqueous perchloric acid and in the presence of 2-propanol have been studied spectrophotometrically with the aid of the initial-rates method. The kinetic order of the oxidant is 2, whereas that of the reductant is not defined. The acidity of the medium has a slight effect on the initial rates (acid catalysis for both L-cysteine and DL-penicillamine and base catalysis for glutathione). An increase of the ionic strength leads to a rise of the initial rate for both L-cysteine and DL-penicillamine, whereas the initial rate for glutathione is insensitive to the ionic strength. The reactions are inhibited by both 2-propanol and dissolved O2 and catalyzed by Mn2+, whereas Ce3+ has almost no effect on them. At low 2-propanol concentration and in the absence of Mn2+ the initial rate vs temperature plots have a minimum at around 20 °C, whereas in the presence of either concentrated 2-propanol or Mn2+ the Arrhenius law is fulfilled. A single mechanism is proposed for the three reactions involving a CrOO2+/thiol complex, CrOOH2+, and CrO2+ as intermediates. The bimolecular rate constants for the reactions of the intermediate CrO2+ with L-cysteine and DL-penicillamine at 25.0 °C have been obtained (around 103 M-1 s-1 in both cases). Some kinetic data for the decomposition of CrOO2+ in the absence of thiol are also given.
