Nucleotide Inhibition of Glyoxalase II Page: 35
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would then undergo rapid hydrolysis resulting in the release of the hydroxyacid to the
solvent. This is consistent with the known lability of acyl-imidazoles (192).
Although researchers for a number of years accepted the proposal for the
catalytic mechanism of Glo-II, recent advances in glyoxalase research have raised doubts
to its validity. Recent reports have identified the presence of two moles of zinc per mole
of Glo-II enzyme purified from Arabidopsis thaliana (191). Comparison of the amino
acid sequence of this enzyme with those from humans and yeast has revealed a region of
homology with that of the zinc-binding motif found in metallo-1-lactamases. Research is
ongoing to define the role of zinc with respect to Glo-II catalytic mechanism and / or
structural integrity. The catalytic mechanism of metallo-3-lactamases is known to
proceed through an acyl-intermediate as well, although the residue acylated in the
lactamase reaction is a serine residue (193) while the proposed acylated residue in Glo-II
is histidine.
1.9.9 Glyoxalase II - Inhibitors
To date, the only natural metabolites that are known to inhibit Glo-II activity are
GSH (168) and the methylglyoxal- derived hemithioacetal substrate for Glo-I (24, 140,
171, 176). The inhibition by GSH is quite weak, with the KI in the high millimolar range
(168). The concentration of the hemithioacetal needed to provide a significant level of
Glo-II inhibition (Ki = 100-200 gM) is far above the predicted physiological
concentration of the hemithioacetal (194). Therefore, the inhibition of Glo-II by these
compounds is not considered to be physiologically relevant.35
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Gillis, Glen S. Nucleotide Inhibition of Glyoxalase II, dissertation, May 1999; Denton, Texas. (https://digital.library.unt.edu/ark:/67531/metadc2183/m1/44/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; .