Reversible cyclization ofS-(2-oxo-2-carboxyethyl)-L-homocysteine to cystathionine ketimine
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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.
KeywordsAmino acids Ketimine Cystathionine
high performance liquid chromatography
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- Costa M, Pensa B, Cavallini D (1984) Ketimine formation by interacting L-cystathionine with glyoxylic acid. IRCS Med Sci 12: 468–469Google Scholar
- Costa M, Pensa B, Blarzino C, Cavallini D (1985) New enzymatic changes of L-cystathionine catalyzed by bovine tissue extracts. Physiol Chem Phys 17: 107–111Google Scholar
- Matarese RM, Pecci L, Ricci G, Cavallini D (1984) Gas-chromatographic determination of thiazine and thiazepine derivatives of biological interest. J Chromatogr 294: 413–418Google Scholar
- Pecci L, Costa M, Pinnen F, Antonucci A, Cavallini D (1988b) Properties of the phenylthiohydantoine derivatives of some sulfur containing cyclic amino acids. Physiol Chem Phys Med NMR 20: 199–203Google Scholar
- Watanabe H, Fujita Y, Sugahara K, Kodama H, Ohmori S (1991) Identification of Nac-HCPC and Nac-β-CEC, and qualitative analyses of sulfur amino acids in the urine of a patient with cystathioninuria using liquid chromatography/atmospheric pressure ionization mass spectrometry. Biol Mass Spectr 20: 602–608Google Scholar