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S-Adenosylhomocysteine Analogue of a Fairy Chemical, Imidazole-4-carboxamide, as its Metabolite in Rice and Yeast and Synthetic Investigations of Related Compounds
During the course of our investigations of fairy chemicals (FCs), we found S-ICAr-H (8a), as a metabolite of imidazole-4-carboxamide (ICA) in rice and yeast (Saccharomyces cerevisiae). In order to determine its absolute configuration, an efficient synthetic method of 8a was developed. This synthetic strategy was applicable to the preparation of analogues of 8a that might be biologically very important, such as S-ICAr-M (9), S-AICAr-H (10), and S-AICAr-M (11).
Ouchi, Hitoshi,Namiki, Takuya,Iwamoto, Kenji,Matsuzaki, Nobuo,Inai, Makoto,Kotajima, Mihaya,Wu, Jing,Choi, Jae-Hoon,Kimura, Yoko,Hirai, Hirofumi,Xie, Xiaonan,Kawagishi, Hirokazu,Kan, Toshiyuki
supporting information
p. 453 - 458
(2021/02/05)

Reduction of an asymmetric Pt(IV) prodrug fac-[Pt(dach)Cl3(OC(=O)CH3)] by biological thiol compounds: kinetic and mechanistic characterizations
An asymmetric Pt(IV) prodrug fac-[Pt (dach)Cl3(OC(=O)CH3)] (dach = 1,2-diaminocyclohexane) was synthesized, and the reduction of the Pt(IV) prodrug by three biological thiols glutathione (GSH), cysteine (Cys) and homocysteine (Hcy) was investigated by a stopped-flow spectrometer. All the reductions were followed by an overall second-order reaction with first-order in both [Pt(IV)] and [thiol]. The reduction of the Pt(IV) prodrug occurred through a chloride bridge (Pt-Cl-S) mediated two electron transfer process. Therefore, the coordinated chloride possesses a better bridging effect than the oxygen atom from the coordinated –CH3COO? of the Pt(IV) prodrug. A reactivity trend of k′Cys > k′GSH > k′Hcy is found, illustrating that the reactivity is followed by the trend of Cys > GSH > Hcy in pH 7.4 buffer. Graphical abstract: Transition state is formed between the axially coordinated chloride of the platinum(IV) complex and the sulfur atom from the thiol/thiolate group of Cys/Hcy/GSH.[Figure not available: see fulltext.].
Huo, Shuying,Ma, Dongying,Song, Changying,Sun, Jingjing,Wang, Yafang
p. 623 - 631
(2021/11/22)

Continuous production method DL-cysteine thiolactone hydrochloride (by machine translation)
The method comprises the following steps DL - reacting, methionine as raw material :(1) with DL - sulfuric acid continuously into a liquid-liquid-phase micro-channel reactor to generate, high-cysteine hydrochloride 15-18mol/L containing DL - high-cysteine hydrochloride in a hydrochloric acid system through dehydration condensation to obtain, high cystine hydrochloride DL - in a continuous circulation reaction . high cystine, is obtained by carrying out a continuous circulation reaction to a cathode chamber, DL - of a plate-and-frame type electrolytic cell in a hydrochloric acid system through a continuous circulation reaction to complete DL - collection of cysteine hydrochloride in a hydrochloric acid system through dehydration and condensation reaction, so as to form DL - high-cysteine hydrochloride in the next step; DL - (1) ;(2). The. method comprises the following steps of: continuously circulating the cathode, solution, from, the liquid-phase micro-channel reactor; and carrying out a reduction reaction in a hydrochloric acid system through a liquid-liquid-phase micro-channel reactor. (by machine translation)
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Paragraph 0039-0063

(2020/04/22)

METHOD OF PRODUCING S-ICA RIBOSYLHOMOCYSTEINE
PROBLEM TO BE SOLVED: To provide novel techniques regarding a method of producing S-ICA ribosylhomocysteine. SOLUTION: A method of producing a compound represented by formula (1) or a salt thereof comprises reacting a compound represented by formula (2) with a compound represented by formula (3) to generate a compound represented by formula (4), and subjecting the obtained compound represented by formula (4) to a treatment of removing a protecting group. SELECTED DRAWING: None COPYRIGHT: (C)2020,JPOandINPIT
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Paragraph 0055-0057

(2020/02/14)

Crystal-facet-dependent denitrosylation: Modulation of NO release from S-nitrosothiols by Cu2O polymorphs
Nitric oxide (NO), a gaseous small molecule generated by the nitric oxide synthase (NOS) enzymes, plays key roles in signal transduction. The thiol groups present in many proteins and small molecules undergo nitrosylation to form the corresponding S-nitrosothiols. The release of NO from S-nitrosothiols is a key strategy to maintain the NO levels in biological systems. However, the controlled release of NO from the nitrosylated compounds at physiological pH remains a challenge. In this paper, we describe the synthesis and NO releasing ability of Cu2O nanomaterials and provide the first experimental evidence that the nanocrystals having different crystal facets within the same crystal system exhibit different activities toward S-nitrosothiols. We used various imaging techniques and time-dependent spectroscopic measurements to understand the nature of catalytically active species involved in the surface reactions. The denitrosylation reactions by Cu2O can be carried out multiple times without affecting the catalytic activity.
Ghosh, Sourav,Roy, Punarbasu,Prasad, Sanjay,Mugesh, Govindasamy
p. 5308 - 5318
(2019/05/29)

Colorimetric and fluorometric determination of homocysteine and cysteine
Colorimetric and fluorometric methods are disclosed for the rapid, accurate, selective, and inexpensive detection of homocysteine, or of homocysteine and cysteine, or of cysteine. The methods may be employed with materials that are readily available commercially. The novel methods are selective for homocysteine, for cysteine, or for total homocysteine and cysteine, and do not cross-react substantially with chemically-related species such as glutathione. The homocysteine-selective method does not have substantial cross-reactivity to the very closely related species cysteine. The cysteine-selective method does not have substantial cross-reactivity to the very closely related species homocysteine. The methods may be used, for example, in a direct assay of human blood plasma for homocysteine levels.
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Page/Page column 8; 9

(2015/12/18)

METHOD FOR PREPARING AN AMINO ACID FROM 2 AMINOBUTYROLACTONE
The invention relates to a method for preparing an amino acid, or its salts, from 2-aminobutyrolactone (2ABL), said amino acid fitting the formula I, XCH2CH2CHNH2COOH, wherein X is such that X? represents a nucleophilic ion, according to which N-carboxylation of 2-aminobutyrolactone (2ABL) is achieved with carbon dioxide, and the thereby obtained 2ABL carbamate is reactive with an XH reagent or its salts.
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Paragraph 0031; 0032; 0033; 0034; 0035; 0036

(2013/07/25)

The development of a new class of inhibitors for betaine-homocysteine S-methyltransferase
Betaine-homocysteine S-methyltransferase (BHMT) is an important zinc-dependent methyltransferase that uses betaine as the methyl donor for the remethylation of homocysteine to form methionine. In the liver, BHMT performs to half of the homocysteine remethylation. In this study, we systematically investigated the tolerance of the enzyme for modifications at the "homocysteine" part of the previously reported potent inhibitor (R,S)-5-(3-amino-3-carboxy-propylsulfanyl)-pentanoic acid (1). In the new compounds, which are S-alkylated homocysteine derivatives, we replaced the carboxylic group in the "homocysteine" part of inhibitor 1 with different isosteric moieties (tetrazole and oxadiazolone); we suppressed the carboxylic negative charge by amidations; we enhanced acidity by replacing the carboxylate with phosphonic or phosphinic acids; and we introduced pyrrolidine steric constraints. Some of these compounds display high affinity toward human BHMT and may be useful for further pharmacological studies of this enzyme. Although none of the new compounds were more potent inhibitors than the reference inhibitor 1, this study helped to completely defi ne the structural requirements of the active site of BHMT and revealed the remarkable selectivity of the enzyme for homocysteine.
Pi?ha, Jan,Vaňek, Václav,Budě??sińsky, Milo?,Mlad?ková, Jana,Garrow, Timothy A.,Ji??acek, Ji??i
p. 256 - 275
(2013/10/01)

Identification and characterization of the first ovothiol biosynthetic Enzyme
Ovothiols are histidine-derived thiols that were first isolated from marine invertebrates. We have identified a 5-histidylcysteine sulfoxide synthase (OvoA) as the first ovothiol biosynthetic enzyme and characterized OvoAs from Erwinia tasmaniensis and Trypanosoma cruzi. Homologous enzymes are encoded in more than 80 genomes ranging from proteobacteria to animalia.
Braunshausen, Andrea,Seebeck, Florian P.
supporting information; experimental part
p. 1757 - 1759
(2011/04/15)

Modulation of homocysteine toxicity by S-nitrosothiol formation: A mechanistic approach
The metabolic conversion of homocysteine (HCYSH) to homocysteine thiolactone (HTL) has been reported as the major cause of HCYSH pathogenesis. It was hypothesized that inhibition of the thiol group of HCYSH by S-nitrosation will prevent its metabolic conversion to HTL. The kinetics, reaction dynamics, and mechanism of reaction of HCYSH and nitrous acid to produce S-nitrosohomocysteine (HCYSNO) was studied in mildly to highly acidic pHs. Transnitrosation of this non-protein-forming amino acid by 5-nitrosoglutathione (GSNO) was also studied at physiological pH 7.4 in phosphate buffer. In both cases, HCYSNO formed quantitatively. Copper ions were found to play dual roles, catalyzing the rate of formation of HCYSNO as well as its rate of decomposition. In the presence of a transition-metal ions chelator, HCYSNO was very stable with a halflife of 198 h at pH 7.4. Nitrosation by nitrous acid occurred via the formation of more powerful nitrosating agents, nitrosonium cation (NO +) and dinitrogen trioxide (N2O3). In highly acidic environments, NO+ was found to be the most effective nitrosating agent with a first-order dependence on nitrous acid. N 2O3 was the most relevant nitrosating agent in a mildly acidic environment with a second-order dependence on nitrous acid. The bimolecular rate constants for the direct reactions of HCYSH and nitrous acid, N2O3, and NO+were 9.0 × 10-2, 9.50 × 103, and 6.57 × 1010 M-1 s-1, respectively. These rate constant values agreed with the electrophilic order of these nitrosating agents: HNO2 2O3 +. Transnitrosation of HCYSH by GSNO produced HCYSNO and other products including glutathione (reduced and oxidized) and homocysteineglutathione mixed disulfide. A computer modeling involving eight reactions gave a good fit to the observed formation kinetics of HCYSNO. This study has shown that it is possible to modulate homocysteine toxicity by preventing its conversion to a more toxic HTL by S-nitrosation.
Morakinyo, Moshood K.,Strongin, Robert M.,Simoyi, Reuben H.
experimental part
p. 9894 - 9904
(2011/08/08)

A study of the glutathione metaboloma peptides by energy-resolved mass spectrometry as a tool to investigate into the interference of toxic heavy metals with their metabolic processes
To better understand the fragmentation processes of the metal-biothiol conjugates and their possible significance in biological terms, an energy-resolved mass spectrometric study of the glutathione conjugates of heavy metals, of several thiols and disulfides of the glutathione metaboloma has been carried out. The main fragmentation process of γ-glutamyl compounds, whether in the thiol, disulfide, thioether or metal-bis-thiolate form, is the loss of the γ-glutamyl residue, a process which ERMS data showed to be hardly influenced by the sulfur substitution. However, loss of the γ-glutamyl residue from the mono-S-glutathionyl-mercury (II) cation is a much more energetic process, possibly pointing at a strong coordination of the carboxylic group to the metal. Moreover, loss of neutral mercury from ions containing the γ-glutamyl residue to yield a sulfenium cation was a much more energetic process than those not containing them, suggesting that the redox potential of the thiol/disulfide system plays a role in the formal reduction of the mercury dication in the gas phase. Occurrence of complementary sulfenium and protonated thiol fragments in the spectra of protonated disulfides of the glutathione metaboloma mirrors the thiol/disulfide redox process of biological importance. The intensity ratio of the fragments is proportional to the reduction potential in solution of the corresponding redox pairs. This finding has allowed the calculation of the previously unreported reduction potentials for the disulfide/thiol pair of cysteinylglycine, thereby confirming the decomposition scheme of bis- and mono-S-glutathionyl-mercury (II) ions. Finally, on the sole basis of the mass spectrometric fragmentation of the glutathione-mercury conjugates, and supported by independent literature evidence, an unprecedented mechanism for mercury ion-induced cellular oxidative stress could be proposed, based on the depletion of the glutathione pool by a catalytic mechanism acting on the metal (II)-thiol conjugates and involving as a necessary step the enzymatic removal of the glutamic acid residue to yield a mercury (II)-cysteinyl-glycine conjugate capable of regenerating neutral mercury through the oxidation of glutathione thiols to the corresponding disulfides. Copyright
Rubino, Federico Maria,Pitton, Marco,Brambilla, Gabri,Colombi, Antonio
p. 1578 - 1593
(2007/10/03)

Characterization of the disulfides of bio-thiols by electrospray ionization and triple-quadrupole tandem mass spectrometry
Glutathione and other intracellular low molecular mass thiols act both as the major endogenous antioxidant and redox buffer system and, as recently highlighted, as an important regulator of cellular homeostasis. Such cellular functions are mediated by protein thiolation, a newly recognized post-translational modification which involves the formation of mixed disulfides between GSH and key disulfide-linked Cys residues in the native protein structure. It is also well known that thiol-seeking heavy metals, such as mercury, cadmium and lead, may interfere in this regulatory system, thus disrupting the cellular functioning. To identify such mixed disulfides in order to investigate their biological role, 15 homo- and heterodimeric disulfides were prepared by air oxidation of binary mixtures containing cysteine, homocysteine, penicillamine, N-acetylcysteine, N-acetylpenicillamine and glutathione and their protonated molecules were characterized by mass spectrometry. Collisionally activated unimolecular decomposition of protonated homo- and heterodimeric disulfides generated by electrospray ionization gives rise to fission of the disulfide system both between the two sulfur atoms and across the C-S bonds, to yield structurally specific fragments which allow one to define the structure of the compounds and to discriminate between isomeric compounds. Fission between the sulfur atoms yields a pair of R-S? ions and, in some cases, also the complementary fragments corresponding to the protonated amino acids. Fission across the C-S bonds mainly occurs in the disulfides of N-acetylcysteine and N-acetylpenicillamine and gives rise to non-S-containing fragments formally similar to those obtained from some mercapturic acids. The complementary fragments, formally connected as R-S-S+ ions are also observed. Fragmentation of glutathione disulfides mainly shows the characteristic loss of the terminal γ-linked glutamic acid and little, if any, fragmentation of the disulfide system. Copyright
Rubino, Federico Maria,Verduci, Cinzia,Giampiccolo, Rosario,Pulvirenti, Salvatore,Brambilla, Gabri,Colombi, Antonio
p. 1408 - 1416
(2007/10/03)

Reaction of ascorbic acid with S-nitrosothiols: Clear evidence for two distinct reaction pathways
Ascorbate reacts with S-nitrosothiols generally, in the pH range 3-13 by way of two distinct pathways, (a) at low [ascorbate], typically below ～1 × 10-4 mol dm-3 which leads to the formation of NO and the disulfide, and (b) at higher [ascorbate] when the products are the thiol and NO. Reaction (a) is Cu2+-dependent, and is completely cut out in the presence of EDTA, whereas reaction (b) is totally independent of [Cu2+] and takes place readily whether EDTA is present or not. For S-nitrosoglutathione (GSNO) the two reactions can be made quite separate, although for some reactants the two reactions overlap. In reaction (a), ascorbate acts as a reducing agent, generating Cu+ from Cu2+, which in turn reacts with RSNO forming initially NO, Cu2+ and RS-. The latter can then play the role of reducing agent for Cu2+, leading to disulfide formation. Ascorbate will initiate reaction when the free thiolate has initially been reduced to a very low level by the synthesis of RSNO from a large excess of nitrous acid over the thiol. Reaction (b) is interpreted in terms of nucleophilic attack by ascorbate at the nitroso-nitrogen atom, leading to thiol and O-nitrosoascorbate which breaks up, by a free-radical pathway, to give dehydroascorbic acid and NO. A similar pathway is the accepted mechanism in the literature for the nitrosation of ascorbate by nitrous acid and alkyl nitrites. The rate constant for the Cu2+-independent pathway increases sharply with pH and analysis of the variation of the rate constant with pH identifies a reaction pathway via both the mono- and di-anion forms of ascorbate, with the latter being the more reactive. As expected the entropy of activation is large and negative. Some aspects of structure-reactivity trends are discussed.
Holmes, Anthony J.,Williams, D. Lyn H.
p. 1639 - 1644
(2007/10/03)

The first asymmetric syntheses of L-homocysteine and L-homocystine
Asymmetric syntheses of L-homocysteine 1 and L-homocystine 2 are described. Alkylation of the carbanion derived from Schollkopf reagent 3 and ensuing hydrolyses gave S-triphenylmethyl-L-homocysteine 6. Removal of the triphenylmethyl group gave L-homocysteine 1 and subsequent oxidation provided L-homocystine 2.
Adamczyk, Maciej,Fishpaugh, Jeffrey R.,Thiruvazhi, Mohan
p. 4151 - 4156
(2007/10/03)

Catalysis by Cu2+ of nitric oxide release from S-nitrosothiols (RSNO)
The decomposition of a range of S-nitrosothiols (thionitrites) RSNO, based on cysteine derivatives, yields in water at pH 7.4 nitrite ion quantitatively.If oxygen is rigorously excluded then no nitrite ion is formed and nitric oxide can be detected using an NO-probe.The reaction is catalysed by trace quantities of Cu2+ (there is often enough present in distilled water samples) and also to a lesser extent by Fe2+, but not by Zn2+, Cu2+, Mg2+, Ni2+, Co2+, Mn2+, Cr3+ or Fe3+.The rate equation (measuring the disappearance of the absorption at ca. 350 nm due to RSNO) was established as v = k*2+> + k' over a range of 2+> typically 5-50 μmol dm-3.The constant term k' represents the component of the rate due to residual Cu2+ in the solvent and buffer components, together with the spontaneous thermal reaction.Decomposition can be virtually halted by the addition of EDTA.Reactions carried out in the presence of N-methylaniline gave a quantitative yield of N-methyl-N-nitrosoaniline, but a negligible yield when oxygen was rigorously excluded.Values of the second-order rate constant k were obtained for a range of S-nitrosothiols.Reactivity is highest for the S-nitrosothiols derived from cysteamine and penicillamine, when Cu2+ can be complexed both with the nitrogen atom of the nitroso group and the nitrogen atom of the amino group, via a six-membered ring intermediate.If there is no amino (or other electron donating group) present, reaction is very slow (as for RSNO derived from a tert-butyl sulfide).N-Acetylation of the amino group reduces the reactivity drastically as does the introduction of another CH2 group in the chain.There is evidence of a significant gem-dimethyl effect.Kinetic results using the S-nitrosothiols derived from mercaptoacetic, thiolactic and thiomalic acids suggests that coordination can also occur via one of the oxygen atoms of the carboxylate group.EPR experiments which examined the Cu2+ signal showed no spectral change during the reaction suggesting that the mechanism does not involve oxidation and reduction with Cu2+ Cu+ interconversion.
Askew, Stuart C.,Barnett, D. Jonathan,McAninly, John,Williams, D. Lyn H.
p. 741 - 746
(2007/10/02)

Kinetics of one-electron oxidation of thiols and hydrogen abstraction by thiyl radicals from α-amino C-H bonds
One-electron oxidation of cysteine, homocysteine, and glutathione by azide radical in alkaline solution (pH 10.5), where both the amino and the SH groups are deprotonated, has been investigated by pulse radiolysis. Reducing α-aminoalkyl radicals (?CR), which are formed via intramolecular rearrangement of thiyl radicals, were detected using methylviologen as oxidant in the kinetic analysis. The general scheme of the reactions is sketched. Thiyl radicals either equilibrate with RSSR?- in reaction 5, RS? + RS- = RSSR?-, or undergo intramolecular transformation via equilibrium 6, RS? = ?CR. At pH 10.5, equilibrium 6 is completely shifted to the right, resulting in α-aminoalkyl radical formation. The rate constants in the reaction scheme for cysteine, homocysteine, and glutathione were measured. With the rate constants obtained, the decay kinetics of RSSR?- into ?CR was simulated, and it agreed with that measured at 420 nm. At pH 10.5, the first-order rate constants for the transformation (k6) were determined to be 2.5 × 104, 1.8 × 105 and 2.2 × 105 s-1 for cysteine, homocysteine, and glutathione, respectively. The rate constants for intermolecular hydrogen abstraction by thiyl radicals from α-amino C-H bonds of alanine and glycine were determined at the same pH to be 7.7 × 105 and 3.2 × 105 M-1 s-1, respectively. Thermodynamic estimation places the reduction potential E°(H2NC(CO2-)CH3-, H+/H2NCH(CO2-)CH3) at ca. 1.22 V, which implies a rather weak tertiary C-H bond in the anion of α-amino acids. Thus, an intramolecular hydrogen abstraction mechanism for the transformation of thiyl radical to α-amino carbon-centered radical is postulated. Molecular geometry plays an important part in deciding the transformation rates (k6,) of different thiyl radicals.
Zhao, Rong,Lind, Johan,Merényi, Gábor,Eriksen, Trygve E.
p. 12010 - 12015
(2007/10/03)

Preparations of Optically Active Homocysteine and Homocystine by Asymmetric Transformation of (RS)-1,3-Thiazane-4-carboxylic Acid
DL-Homocysteine from (RS)-homocysteine thiolactone hydrochloride was subjected to reaction with formaldehyde in acetic acid to give (RS)-1,3-thiazane-4-carboxylic acid monohydrate .An asymmetric transformation of (RS)-THA*H2O was achieved via salt formation with optically active tartaric acid in the presence of salicylaldehyde in acetic acid.The (R)- and (S)-THA obtained, respectively, from the salt of (R)-THA with (2R,3R)-tartaric acid and its enantiomeric salt were treated with hydroxylamine hydrochloride to give D- and L-Hcy of 100percent optical purity, respectively, in 50percent yield from (RS)-HTL*HCl.Oxidation of D- and L-Hcy with hydrogen peroxide gave D- and L-homocystine, respectively, in 47percent yield.
Miyazaki, Hideya,Ohta, Atsushi,Kawakatsu, Nobuyuki,Waki, Yukitaka,Gogun, Yasuhiro,et al.
p. 536 - 540
(2007/10/02)

A Model of the Cobalamin-independent Methionine Synthase Reaction
Homocysteine is converted to methionine via a nonenzymatic methyl transfer from a 5-methyltetrahydrofolate model bearing a positive charge at N(5).
Hilhorst, Ellen,Chen, Tjoe B. R. A.,Pandit, Upendra K.
p. 881 - 882
(2007/10/02)

Kinetics and Equilibria of Thiol/Disulfide Interchange Reactions of Selected Biological Thiols and Related Molecules with Oxidized Glutathione
Rate constants for reaction of coenzyme A and cysteine with oxidized glutathione (GSSG) and equilibrium constants for the reaction of coenzyme A, cysteine, homocysteine, cysteamine, and related thiols with GSSG by thiol/disulfide interchange were determined over a range of pD values by NMR spectroscopy.The rate constants for reaction of the thiolate anion forms of coenzyme A and cysteine with GSSG suggest that reduction of GSSG by coenzyme A and cysteine is a mechanistically uncomplicated SN2 reaction.Equilibrium constants for the thiol/disulfide interchange reactions show a strong dependence on the Bronsted basicity of the thiolate anion.In a similar way, ΔE0', the difference between the half-cell potentials for the RSSR/RSH and GSSG/GSH redox couples, is linearly dependent on the difference between the pKA values of RSH and glutathione: ΔE0' = 64ΔpKA - 7.7 where ΔE0' is in units of mV.The reducing strength at a given pH is also determined by the fraction of the thiol present in the reactive thiolate form.At pD 7, the half-cell potentials for coenzyme A, cysteine, homocysteine, and cysteamine are close to that of glutathione, the major intracellular thiol redox system, which suggests that small changes in the intracellular redox potential can cause significant changes in the intracellular distribution of these biological thiols between their reduced and oxidized forms.
Keire, David A.,Strauss, Erin,Guo, Wei,Noszal, Bela,Rabenstein, Dallas L.
p. 123 - 127
(2007/10/02)