Gas-chromatographic determination of enantiomeric composition of amino acid mixtures

Saporovskaya, M. B.; Paskonova, E. A.; Nikitina, S. B.; Vitt, S. V.; Belikov, V. M.

doi:10.1007/bf00921162

Cited by 1 publication

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“…The eluate was then evaporated to dryness. The ratio of enantiomers was determined by GLC according to [8]. The optical purity of the L -[~-~H ] -phenylalanine was 98%, which does not differ from the optical purity of the initial nondeuterated product.…”

Section: Stereochemistry Of Phenylalanine and Tryptophan Isotope Exchmentioning

confidence: 99%

Tyrosine phenol‐lyase from Citrobacter intermedius

Adriaensens

Box

Martens

et al. 1988

European Journal of Biochemistry

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L-Amino acids are competitive inhibitors of tyrosine phenol-lyase from Citrohucter intermedius. For nonbranched amino acids the correlation exists between -RTlnK, and side-chain hydrophobicity. Aspartic and glutamic acids are anomalously potent inhibitors taking into account low hydrophobicity of their side chains. This suggests the presence of an electrophilic group in the active site which interacts with the terminal carboxylic group of aspartic or glutamic acids. Tyrdmine, a-phenylethylamine and tryptamine do not display detectable inhibition. The esters and amides of aromatic L-amino acids, D-phenylalanine and D-tryptophan are competitive inhibitors. The enzymatic isotope exchange of the a-proton in 'H20 was observed only in the case of L-amino acids. For L-phenylalanine and L-tryptophan it was shown to proceed with complete retention of configuration. The substrate specificity of tyrosine phenol-lyase is controlled during the stage of phenol elimination. The OH group in the pura position of the ring is necessary for this stage to proceed. The same stage is also sensitive to the steric parameters of the substituent in the ring which ensures the second factor of control. When all the requirements of substrate specificity are fulfilled (L-tyrosine, 3-fluoro-~-tyrosine) the 'key' phenol-elimination step is not the rate-limiting one, the reaction velocity being determined by the preceding a-proton abstraction.Tyrosine phenol-lyase (L-tyrosine phenol-lyase, deaminating) is an interesting pyridoxal-P-dependent lyase which catalyses the transformation of L-tyrosine to pyruvate, phenol and ammonia [l]. The enzyme is produced by a number of bacteria grown on media containing L-tyrosine. The reversibility of the main reaction (Eqn l), at high concentrations of products, may be used for the synthesis of L-tyrosine or H o~c H~-~H -c o o -+ H~O~ NH:

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Section: Stereochemistry Of Phenylalanine and Tryptophan Isotope Exchmentioning

confidence: 99%