NUKLEONIKA 2006, 51(Suppl. 2):s7-s11

CARBON ISOTOPE EFFECTS IN THE STUDIES OF THE MECHANISM OF ACTION OF TYROSINE PHENOL-LYASE

Wojciech Augustyniak, Ryszard Kański, Marianna Kańska

Department of Chemistry, University of Warsaw, 1 Pasteura Str., 02-093 Warsaw, Poland

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.