Widespread, Reversible Cysteine Modification by Methylglyoxal Regulates Metabolic Enzyme Function

Methylglyoxal (MGO),
a reactive metabolite byproduct
of glucose
metabolism, is known to form a variety of posttranslational modifications
(PTMs) on nucleophilic amino acids. For example, cysteine, the most
nucleophilic proteinogenic amino acid, forms reversible hemithioacetal
and stable mercaptomethylimidazole adducts with MGO. The high reactivity
of cysteine toward MGO and the rate of formation of such modifications
provide the opportunity for mechanisms by which proteins and pathways
might rapidly sense and respond to alterations in levels of MGO. This
indirect measure of alterations in glycolytic flux would thereby allow
disparate cellular processes to dynamically respond to changes in
nutrient availability and utilization. Here we report the use of quantitative
LC–MS/MS-based chemoproteomic profiling approaches with a cysteine-reactive
probe to map the proteome-wide landscape of MGO modification of cysteine
residues. This approach led to the identification of many sites of
potential functional regulation by MGO. We further characterized the
role that such modifications have in a catalytic cysteine residue
in a key metabolic enzyme and the resulting effects on cellular metabolism.