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  • 1
    Electronic Resource
    Electronic Resource
    Identification of 1,4-thiomorpholine-3-carboxylic acid (TMA) in normal human urine
    Amsterdam : Elsevier
    FEBS Letters 250 (1989), S. 75-77 
    Details
    ISSN: 0014-5793
    Keywords: (Human) ; Cyclic imino acid ; Sulfur compound ; Thiomorpholine-3-carboxylic acid, 1,4- ; Urine
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0014-5793(89)80688-X
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  • 2
    Electronic Resource
    Electronic Resource
    The reducing activity of S-aminoethylcysteine ketimine and similar sulfur-containing ketimines
    Amsterdam : Elsevier
    Biochemical and Biophysical Research Communications 183 (1992), S. 481-486 
    Details
    ISSN: 0006-291X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0006-291X(92)90507-H
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  • 3
    Electronic Resource
    Electronic Resource
    Aminoethylcysteine Ketimine Decarboxylated Dimer Inhibits Mitochondrial Respiration by Impairing Electron Transport at Complex I Level
    Amsterdam : Elsevier
    Biochemical and Biophysical Research Communications 199 (1994), S. 755-760 
    Details
    ISSN: 0006-291X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1006/bbrc.1994.1293
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  • 4
    Electronic Resource
    Electronic Resource
    Aminoethylcysteine Ketimine-Decarboxylated Dimer Protects Submitochondrial Particles from Lipid Peroxidation at a Concentration Not Inhibitory of Electron Transport
    Amsterdam : Elsevier
    Biochemical and Biophysical Research Communications 205 (1994), S. 264-268 
    Details
    ISSN: 0006-291X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1006/bbrc.1994.2659
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  • 5
    Electronic Resource
    Electronic Resource
    The oxidation of sulfur containing cyclic ketimines The sulfoxide is the main product of S-aminoethyl-cysteine ketimine autoxidation (1993)
    Springer
    Amino acids 5 (1993), S. 23-32 
    Details
    ISSN: 1438-2199
    Keywords: Amino acids ; Aminoethylcysteine ; Thialysine ; Ketimines ; Chondrine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The products of autoxidation of S-aminoethyl-L-cysteine ketimine (AECK) have been analysed with the amino acid analyzer, with thin layer chromatography and with high performance liquid chromatography. Under the conditions of the assay (pH 8.5, 38°C, O2 bubbling) AECK is almost totally oxidized in 1.5 hours. Among the final products a component running fast in HPLC, named Cx1, has been isolated, reduced with NaBH4 and analysed. Reduced Cx1 resulted to show the same properties of synthetic thiomorpholine-3-carboxylic acid-S-oxide, known in the past literature with the name of “chondrine”. On the basis of these results and by specific chromatographic tests, Cx1 has been identified as the sulfoxide of AECK. Among the other autoxidation products, thiomorpholine-3-one has been identified. The detection, after HCl hydrolysis, of glyoxylic acid and mesoxalic semialdehyde together with cysteamine indicates that compounds provided with easily cleavable S-C bonds, possibly thiohemiacetals or (and) thioesters, are the likely intermediates for other products. AECK sulfoxide and thiomorpholine-3-one are relatively stable and cannot be taken as the main intermediates for the remaining oxidation products.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00806189
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  • 6
    Electronic Resource
    Electronic Resource
    An insight in the mechanism of the aminoethylcysteine ketimine autoxidation (1996)
    Springer
    Amino acids 10 (1996), S. 379-390 
    Details
    ISSN: 1438-2199
    Keywords: Amino acids ; Aminoethylcysteine ; Ketimines ; Iron chelates ; Autoxidation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Oxidation of aminoethylcysteine ketimine (AECK) is followed by the change of 296nm absorbance, by the O2 consumption and by the HPLC analysis of the oxidation products. The oxidation is strongly inhibited by the addition of superoxide dismutase (SOD) but not by hydroxyl radical scavengers or catalase. Addition of EDTA or o-phenanthroline (OPT) favours the oxidation, probably by keeping contaminating metals in solution at the pH studied. Addition of Fe3+ ions strongly accelerates the oxidation in the presence of EDTA or OPT. AECK reacts stoichiometrically with OPT-Fe3+ complex producing the Fe2+ complex which is not reoxidised by bubbling O2. HPLC analyses of the final oxidation products reacting with 2,4-dinitrophenylhydrazine (DNPH) confirm the AECK sulfoxide as the main product of the slow spontaneous oxidation. The detection of other oxidation products when the reaction is speeded up by the addition of the OPT-Fe3+ complex, suggests that the oxidation takes place essentially on the carbon portion of the AECK molecule in the side of the double bond. On the basis of the results presented here, a scheme of reactions is illustrated which starts with the transfer of one electron from AECK to a contaminating metal ion (possibly Fe3+) producing the radical AECK• as the initiator of a self propagating reaction. The radical AECK• reacting with O2 starts a series of reactions accounting for most of the products detected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00805865
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  • 7
    Electronic Resource
    Electronic Resource
    Novel findings on the copper catalysed oxidation of cysteine (1997)
    Springer
    Amino acids 13 (1997), S. 355-367 
    Details
    ISSN: 1438-2199
    Keywords: Amino acids ; Cysteine ; Copper catalysis ; Cuprous complex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The oxidation of cysteine (RSH) has been studied by using O2, ferricytochrome c (Cyt c) and nitro blue tetrazolium (NBT) as electron acceptors. The addition of 200μM CuII to a solution of 2mM cysteine, pH 7.4, produces an absorbance with a peak at 260 nm and a shoulder at 300 nm. Generation of a cuprous bis-cysteine complex (RS-CuI-SR) is responsible for this absorbance. In the absence of O2 the absorbance is stable for long time while in the presence of air it vanishes slowly only when the cysteine excess is consumed. The neocuproine assay and the EPR analysis show that the metal remains reduced in the course of the oxidation of cysteine returning to the oxidised form at the end of reaction when all RSH has been oxidised to RSSR. Addition of CuII enhances the reduction rate of Cyt c and of NBT by cysteine also under anaerobiosis indicating the occurrence of a direct reduction of the acceptor by the complex. It is concluded that the cuprous bis-cysteine complex (RS-CuI-SR) is the catalytic species involved in the oxidation of cysteine. The novel finding of the stability of the complex together with the metal remaining in the reduced form during the oxidation suggest sulfur as the electron donor in the place of the metal ion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01372599
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  • 8
    Electronic Resource
    Electronic Resource
    Reversible cyclization ofS-(2-oxo-2-carboxyethyl)-L-homocysteine to cystathionine ketimine (1993)
    Springer
    Amino acids 4 (1993), S. 133-140 
    Details
    ISSN: 1438-2199
    Keywords: Amino acids ; Ketimine ; Cystathionine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary S-(2-oxo-2-carboxyethyl)homocysteine (OCEHC), produced by the enzymatic monodeamination of cystathionine, is known to cyclize producing the seven membered ring of cystathionine ketimine (CK) which has been recognized as a cystathionine metabolite in mammals. Studies have been undertaken in order to find the best conditions of cyclization of synthetic OCEHC to CK and for the preparation of solid CK salt product. It has been found that ring closure takes place at alkaline pH and is highly accelerated in 0.5 M phosphate buffer. The sodium salt of CK has been prepared by controlled additions of NaOH to water-ethanol solution of OCEHC under N2 atmosphere. A solid product is obtained which, dissolved in water, shows the spectral features of CK. Solutions of the sodium salt of CK show the presence of a pH depending reversible equilibrium with the open OCEHC form. Plot of the absorbance at 296 nm in function of pH indicates that at pH 9 the compound is completely cyclized while at pH 6 is totally in the open OCEHC form. At intermediate pHs variable ratios between the two forms occur. According to the results obtained by the spectral analysis, HPLC assays of the sodium salt of CK show different patterns depending on the pH of the elution buffer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00805809
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