Search

Halogenated, labeled with deuterium, tritium or doubly labeled with deuterium and tritium in the 3S position of the side chain isotopomers of L-phenylalanine and phenylpyruvic acid were synthesized. Isotopomers of halogenated L-phenylalanine were obtained by addition of ammonia from isotopically enriched buffer solution to the halogenated derivative of (E)-cinnamic acid catalyzed by phenylalanine ammonia lyase. Isotopomers of halogenated phenylpyruvic acid were obtained enzymatically by conversion of the appropriate isotopomer of halogenated L-phenylalanine in the presence of phenylalanine dehydrogenase. As a source of deuterium was used deuterated water, as a source of tritium was used a solution of highly diluted tritiated water. The labeling takes place in good yields and with high deuterium atom% abundance., (© 2023 John Wiley & Sons Ltd.)

Halogenated, labeled with tritium and doubly with deuterium and tritium, derivatives of L-tryptophan, i.e. 5'-bromo-[2-(3)H]-, 5'-bromo-[2-(2)H/(3)H]-, 5'-fluoro-[2-(3)H]-5'-fluoro-[2-(2)H/(3)H]-, 6'-fluoro-[2-(3)H]-, 6'-fluoro-[2-(2)H/(3)H]-L-tryptophan, as well as, L-tyrosine, i.e. 3'-fluoro-[2-(3)H]-, 3'-fluoro-[2-(2)H/(3)H]-, 3'-chloro-[2-(3)H]-, and 3'-chloro-[2-(2)H/(3)H]-L-tyrosine, and also L-phenylalanine, i.e. 2'-fluoro-[(3S)-(3)H]-, 2'-fluoro-[(3S)-(2)H/(3) H]-, 2'-chloro-[(3S)-(3)H]-, 2'-chloro-[(3S)-(2)H/(3)H]-, 4'-chloro-[(3S)-(3)H]-, and 4'-chloro-[(3S)-(2)H/(3)H]-L-phenylalanine were synthesized using enzymatic methods. Isotopomers of L-tryptophan were synthesized by coupling of halogenated indoles with S-methyl-L-cysteine carried out in deuteriated or tritiated incubation media. Labeled halogenated derivatives of L-tyrosine were obtained by the enzymatically supported exchange between halogenated L-tyrosine and isotopic water. Labeled halogenated isotopologues of L-Phe were synthesized by the enzymatic addition of ammonia to halogenated cinnamic acid. As a source of hydrogen tritiated water (HTO) and heavy water (D2O) with addition of HTO were used., (Copyright © 2015 John Wiley & Sons, Ltd.)

Cyclomaltohexaose (α-cyclodextrin) and cyclomaltoheptaose (β-cyclodextrin) as well as their four methyl ether derivatives, that is, hexakis(2,3-di-O-methyl)cyclomaltohexaose, hexakis(2,3,6-tri-O-methyl)cyclomaltohexaose, heptakis(2,3-di-O-methyl)cyclomaltoheptaose, and heptakis(2,3,6-tri-O-methyl)cyclomaltoheptaose were investigated as the additives in the course of enzymatic decomposition of l-phenylalanine catalyzed by phenylalanine ammonia-lyase. Only a few of those additives behaved like classical inhibitors of the enzymatic reaction under investigation because the values of the Michaelis constants that were obtained, as well as the maximum velocity values depended mostly atypically on the concentrations of those additives. In most cases cyclodextrins caused mixed inhibition, both competitive and noncompetitive, but they also acted as activators for selected concentrations. This atypical behaviour of cyclodextrins is caused by three different and independent effects. The inhibitory effect of cyclodextrins is connected with the decrease of substrate concentration and unfavourable influence on the flexibility of the enzyme molecules. On the other hand, the activating effect is connected with the decrease of product concentration (the product is an inhibitor of the enzymatic reaction under investigation). All these effects are caused by the ability of the cyclodextrins to form inclusion complexes., (Copyright © 2011 Elsevier Ltd. All rights reserved.)