The mechanism of the reactions catalyzed by the pyridoxal-phosphate- independent amino acid racemases and epimerases faces the difficult task of deprotonating a relatively low acidicity proton, the amino acid's α-hydrogen, with a relatively poor base, a cysteine. In this work, we propose a mechanism for one of these enzymes, glutamate racemase (MurI), about which many controversies exist, and the roles that its active site residues may play. The titration curves and the pK1/2 values of all of the ionizable residues for different structures leading from reactants to products have been analyzed. From these results a concerted mechanism has been proposed in which the Cys70 residue would deprotonate the α-hydrogen of the substrate while, at the same time, being deprotonated by the Asp7 residue. To study the consistency of this mechanism-classical molecular dynamics (MD) simulations have been carried out along with pK1/2 calculations on the MD-generated structures. © 2007 American Chemical Society.
|Journal||Journal of Physical Chemistry B|
|Publication status||Published - 8 Mar 2007|
Puig, E., Garcia-Viloca, M., González-Lafont, À., Lluch, J. M., & Field, M. J. (2007). New insights into the reaction mechanism catalyzed by the glutamate racemase enzyme: PH titration curves and classical molecular dynamics simulations. Journal of Physical Chemistry B, 111, 2385-2397. https://doi.org/10.1021/jp066350a