E. Boroda, R. Kański, M. Kańska
2006
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0
Influential Citations
2
Citations
Journal
Nukleonika
Abstract
The enzyme tryptophanase (L-tryptophan indole lyase EC 4.1.99.1), TPase, catalyses the decomposition of L-Trp to the corresponding indole, pyruvic acid, and ammonia [12], (Scheme 1). Under certain conditions, there is a possibility of reverse reaction, leading to the formation of L-tryptophan. This enzyme also decomposes L-serine, L-cysteine, S-methyl-L-cysteine, and is often used in the synthesis of L-tryptophan [6]. In the literature, the mechanism of TPase catalysis are well documented [4, 8]. Most of study of them were performed using stopped flow spectroscopy [7, 9, 11] and research with using mutants [10]. One technique often used in studying such a kind of reaction mechanisms is the kinetic isotopic effect method (KIE). By labelling the molecule in different positions and determining primary and secondary KIE’s, it is possible to find out the number of reactive sites and to elucidate the structure of transition state [3]. The purpose of our study was to determine the KIE for the α-hydrogen atom during breaking the bond between indol moiety and the 3-carbon atom in the side chain of L-Trp in the course of decomposition reaction shown in Scheme 1. In this study, we have used an isotopomer of L-Trp, i.e., [2-H]-L-tryptophan, [2-H]L-Trp and the second isotopomer of [1-C]-Ltryptophan, [1-C]-L-Trp, as an internal radiometric Tritium kinetic isotope effects on enzymatic decomposition of L-tryptophan Elzbieta Boroda, Ryszard Kanski, Marianna Kanska