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3 Nukleonika

3 2006

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Tritium kinetic isotope effects on enzymatic decomposition of L-tryptophan

Boroda E., Kański R., Kańska M.

Nukleonika

2006

Vol. 51,suppl.2

17-19

The tritium kinetic isotope effect on position 2 has been determined in the reaction of decomposition of L-tryptophan, L-Trp, catalyzed by enzyme TPase, (EC 4.1.99.1). The numerical values of isotope effects in the course of reaction were obtained by the competitive method using [1-14C]-L-tryptophan as internal radiometric standard.

Synthesis of ring labeled [1'-14C]-L-tyrosine

Kański R., Augustyniak W., Kańska M.

Nukleonika

2006

Vol. 51,suppl.2

13-16

The synthesis of specifically ring labeled isotopomer of L-tyrosine, (l-Tyr), using chemical and enzymatic methods is reported. The carbon-14 labeled [1’-14C]-L-Tyr has been synthesized by a 6-step conversion of [2-14C]-malonic acid into [4’-14C]-phenol and its subsequent condensation with S-methyl-L-cysteine using enzyme tyrosine phenol lyase from Citrobacter freundii.

Carbon isotope effects in the studies of the mechanism of action of tyrosine phenol-lyase

Augustyniak W., Kański R., Kańska M.

Nukleonika

2006

Vol. 51,suppl.2

7-11

12C/14C kinetic isotope effects on the hydrolytic cleavage of tyrosine to phenol and ammonium pyruvate catalyzed by Citrobacter freundii tyrosine phenol-lyase have been determined in positions 2, 3 and ring-1' of L-tyrosine. The competitive method with dual-label approach was applied with 3',5'-ring 3H as remote label. The results revealed the change of the effect on carbon atom in position 2 during the reaction course from the high normal values to low inverse values. On the other hand, the effect values on 3 and ring-1' position remained constant during the reaction course. The discussion of these results regarding the reaction mechanism is presented.