PMID: 6110440Jan 6, 1981Paper

Mechanism of urocanase as studied by deuterium isotope effects and labeling patterns

Biochemistry
R M EganA T Phillips

Abstract

Nicotinamide adenine dinucleotide (NAD) dependent urocanase (4'-imidazolone-5'-propionate hydro-lyase, EC 4.2.1.49) from Pseudomonas putida was found to catalyze an exchange reaction between solvent and the 4'-hydrogen of urocanate or imidazolepropionate at a rate faster than that of overall deuterium was compared to unlabeled urocanate as a substrate, no isotope rate effect was noted. For examination of the possibility of an NAD+-mediated intramolecular hydride transfer of the 4'-hydrogen to a position on the side chain of oxoimidazolepropionate, the origins of hydrogen at positions 2 and 3 in the propionate chain were studied as a function of reaction time and extent of exchange of the 4'-hydrogen. No transfer of hydrogen from the 4' position to the side chain was observed, thereby eliminating mechanisms requiring hydride transfer via NADH between these positions. Catalytic rates in 1H2O vs. 2H2O revealed a 3-fold difference which was ascribed to a rate-limiting proton addition step. Similarly, a 5-fold decrease in Vmax was found for the reverse reaction when oxoimidazole[2,3-2H2]propionate was compared to unlabeled oxoimidazolepropionate. These data support a mechanism involving water addition across the conjugated double bo...Continue Reading

References

Nov 1, 1977·Archives of Biochemistry and Biophysics·A T PhillipsB Lewis
Feb 19, 1975·Biochimica Et Biophysica Acta·M S CohnA T Phillips
Nov 11, 1971·European Journal of Biochemistry·F Kaeppeli, J Rétey
Jan 28, 1980·FEBS Letters·E Gerlinger, J Rétey
Jun 1, 1980·Archives of Biochemistry and Biophysics·P S O'DonnellJ K Hunter
Apr 2, 1963·Biochemical and Biophysical Research Communications·J LUDOWIEG, A LEVY

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Citations

Jun 1, 1989·Journal of Photochemistry and Photobiology. B, Biology·P S O'Donnell, D H Hug
Jan 1, 1983·Archives of Biochemistry and Biophysics·L H Matherly, A T Phillips
May 25, 1982·Biochemistry·L H MatherlyA T Phillips
Jul 1, 1981·European Journal of Biochemistry·E GerlingerJ Rétey

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