Open AccessRole of GldA in dihydroxyacetone and methylglyoxal metabolism of Escherichia coli K12
Author(s) -
Subedi Krishna P.,
Kim Insook,
Kim Junho,
Min Bumchan,
Park Chankyu
Publication year - 2008
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.2007.01032.x
Subject(s) - methylglyoxal , dihydroxyacetone , dihydroxyacetone phosphate , biochemistry , lactoylglutathione lyase , escherichia coli , metabolite , aldolase a , biology , glycerol , chemistry , enzyme , gene
The metabolic pathway involving dihydroxyacetone is poorly characterized although novel enzymes associated with this metabolite have recently been demonstrated. The role of GldA in dihydroxyacetone and methylglyoxal metabolism was investigated by purifying the enzyme and characterizing its catalytic ability using nuclear magnetic resonance (NMR) spectroscopy. At neutral pH, the enzyme exhibits much higher affinities towards dihydroxyacetone, methylglyoxal, and glycolaldehyde than glycerol with K m values of 0.30, 0.50, 0.85, and 56 mM, respectively. This is consistent with NMR data with crude extracts, showing that the conversion from dihydroxyacetone to glycerol by GldA is far more efficient than the reverse reaction. Dihydroxyacetone was found to be lethal at higher concentration with an LC 50 value of 28 mM compared with 0.4 mM of methylglyoxal, while lactaldehyde was found to exhibit significant growth inhibition in Escherichia coli cells. The toxicity of dihydroxyacetone appears to be due to its intracellular conversion to an aldehyde compound, presumably methylglyoxal, since the glyoxalase mutant becomes sensitive to dihydroxyacetone. Based on information that gldA is preceded in an operon by the ptsA homolog and talC gene encoding fructose 6‐phosphate aldolase, this study proposes that the primary role of gldA is to remove toxic dihydroxyacetone by converting it into glycerol.