Abstract
The glyoxalase system is the ubiquitous pathway for the detoxification of methylglyoxal (MG) in the biological systems. It comprises two enzymes, glyoxalase I (GLYI) and glyoxalase II (GLYII), which act sequentially to convert MG into d-lactate, thereby helping living systems get rid of this otherwise cytotoxic byproduct of metabolism. In addition, a glutathione-independent GLYIII enzyme activity also exists in the biological systems that can directly convert MG to d-lactate. Humans and Escherichia coli possess a single copy of GLYI (encoding either the Ni- or Zn-dependent form) and GLYII genes, which through MG detoxification provide protection against various pathological and disease conditions. By contrast, the plant genome possesses multiple GLYI and GLYII genes with a role in abiotic stress tolerance. Plants possess both Ni2+- and Zn2+-dependent forms of GLYI, and studies on plant glyoxalases reveal the various unique features of these enzymes distinguishing them from prokaryotic and other eukaryotic glyoxalases. Through this review, we provide an overview of the plant glyoxalase family along with a comparative analysis of glyoxalases across various species, highlighting similarities as well as differences in the biochemical, molecular, and physiological properties of these enzymes. We believe that the evolution of multiple glyoxalases isoforms in plants is an important component of their robust defense strategies.
Highlights
The research on methylglyoxal (MG) and the glyoxalase pathway was initiated more than 100 years ago and since many discoveries have been made in the field of glyoxalases
Besides the typical glyoxalase pathway that carries out the two-step metabolism of MG to D-lactate via glyoxalase I (GLYI) and glyoxalase II (GLYII) enzymes, living systems possess a glyoxalase III (GLYIII) activity that directly converts MG to D-lactate without even requiring reduced glutathione (GSH) [4,5], otherwise needed as a cofactor for reactions
Copper binding has been reported for human and Arabidopsis DJ-1 proteins; though not required for their GLYIII activity, it is essential for the activation of superoxide dismutase enzyme through copper transfer [24,25]
Summary
The research on methylglyoxal (MG) and the glyoxalase pathway was initiated more than 100 years ago and since many discoveries have been made in the field of glyoxalases. Besides the typical glyoxalase pathway that carries out the two-step metabolism of MG to D-lactate via glyoxalase I (GLYI) and glyoxalase II (GLYII) enzymes, living systems possess a glyoxalase III (GLYIII) activity that directly converts MG to D-lactate without even requiring reduced glutathione (GSH) [4,5], otherwise needed as a cofactor for reactions. 2017, 18, 250 contradict the previous concept of linking Ni2+-dependent activation property of GLYI enzymes to prokaryotes [13] and lately to lower eukaryotes [14], thereby scrapping the previous metal-based classification of GLYI. The metal ions like Cu2+, Fe2+ and Zn2+ have been, shown to have inhibitory effects on the GLYIII activity of Hsp protein from E. coli [4]. Copper binding has been reported for human and Arabidopsis DJ-1 proteins; though not required for their GLYIII activity, it is essential for the activation of superoxide dismutase enzyme through copper transfer [24,25]
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