Effects of alpha-deuteration and of aza and thia analogs of L-tryptophan on formation of intermediates in the reaction of Escherichia coli tryptophan indole-lyase

Biochemistry
M J Sloan, Robert S Phillips

Abstract

Tryptophan indole-lyase catalyzes the hydrolytic cleavage of L-tryptophan to indole and ammonium pyruvate. After the enzyme is mixed with L-tryptophan in the rapid-scanning stopped-flow spectrophotometer, there is an absorbance increase at 505 nm in the pre-steady state attributed to formation of a quinonoid intermediate, which occurs in at least three consecutive first-order phases. Reaction with [alpha-2H]-L-tryptophan results in significant primary kinetic isotope effects on the first two phases, and there is a significant isotope effect on the amplitude of the absorbance increase in the second phase. This result suggests that proton transfer to carbon to form the indolenine intermediate is relatively slow and is probably at least partially rate-determining. Reaction of L-tryptophan in the presence of benzimidazole results in a rapid increase in absorbance in the first phase, followed by a decrease in absorbance in the second phase, with rate constants very similar to those observed without benzimidazole. We have also examined aza and thia analogs of L-tryptophan, with the benzene ring of the indole replaced by pyridine or thiophene. Both 4,5-thiatryptophan and 6,7-thiatryptophan form quinonoid intermediates in the reaction ...Continue Reading

References

Jul 15, 1976·FEBS Letters·C H SuelterE E Snell
Sep 1, 1981·Journal of Bacteriology·M C Deeley, C Yanofsky

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Citations

Apr 11, 2003·Biochimica Et Biophysica Acta·Robert S PhillipsNicolai G Faleev
Jun 23, 2001·Protein Science : a Publication of the Protein Society·N BudisaL Moroder
Nov 18, 2010·Archives of Biochemistry and Biophysics·Robert S PhillipsDouglas Bartlett
Nov 21, 2015·Isotopes in Environmental and Health Studies·Elżbieta WinnickaMarianna Kańska
Mar 11, 1998·Natural Product Reports·P M Dewick
Apr 6, 2002·The Journal of Biological Chemistry·Robert S PhillipsAndrea Mozzarelli

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