Document Type

Article

Language

eng

Publication Date

9-2010

Publisher

American Chemical Society

Source Publication

Biochemistry

Source ISSN

0006-2960

Original Item ID

DOI: 10.1021/bi1010865

Abstract

Arabidopsis thaliana glyoxalase 2-1 (GLX2-1) exhibits extensive sequence similarity with GLX2 enzymes but is catalytically inactive with SLG, the GLX2 substrate. In an effort to identify residues essential for GLX2 activity, amino acid residues were altered at positions 219, 246, 248, 325, and 328 in GLX2-1 to be the same as those in catalytically active human GLX2. The resulting enzymes were overexpressed, purified, and characterized using metal analyses, fluorescence spectroscopy, and steady-state kinetics to evaluate how these residues affect metal binding, structure, and catalysis. The R246H/N248Y double mutant exhibited low level S-lactoylglutathione hydrolase activity, while the R246H/N248Y/Q325R/R328K mutant exhibited a 1.5−2-fold increase in kcat and a decrease in Km as compared to the values exhibited by the double mutant. In contrast, the R246H mutant of GLX2-1 did not exhibit glyoxalase 2 activity. Zn(II)-loaded R246H GLX2-1 enzyme bound 2 equiv of Zn(II), and 1H NMR spectra of the Co(II)-substituted analogue of this enzyme strongly suggest that the introduced histidine binds to Co(II). EPR studies indicate the presence of significant amounts a dinuclear metal ion-containing center. Therefore, an active GLX2 enzyme requires both the presence of a properly positioned metal center and significant nonmetal, enzyme−substrate contacts, with tyrosine 255 being particularly important.

Comments

Accepted version. Biochemistry, Vol. 49, No. 37 (September 2010): 8228-8236. DOI. © 2010 American Chemical Society Publications. Used with permission.

Brian Bennett was affiliated with Medical College of Wisconsin at the time of publication.

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