These authors contributed equally to this work.
Hsp31 of Escherichia coli K-12 is glyoxalase III
Article first published online: 6 JUL 2011
© 2011 Blackwell Publishing Ltd
Volume 81, Issue 4, pages 926–936, August 2011
How to Cite
Subedi, K. P., Choi, D., Kim, I., Min, B. and Park, C. (2011), Hsp31 of Escherichia coli K-12 is glyoxalase III. Molecular Microbiology, 81: 926–936. doi: 10.1111/j.1365-2958.2011.07736.x
- Issue published online: 10 AUG 2011
- Article first published online: 6 JUL 2011
- Accepted manuscript online: 23 JUN 2011 01:56AM EST
- Accepted 9 June, 2011.
Hsp31 encoded by hchA is known as a heat-inducible molecular chaperone. Although structure studies revealed that Hsp31 has a putative catalytic triad consisting of Asp-214, His-186 and Cys-185, its enzymatic function, besides weak amino-peptidase activity, is still unknown. We found that Hsp31 displays glyoxalase activity that catalyses the conversion of methylglyoxal (MG) to d-lactate without an additional cofactor. The glyoxalase activity was completely abolished in the hchA-deficient strain, confirming the relationship between the hchA gene and its enzymatic activity in vivo. Hsp31 exhibits Michaelis–Menten kinetics for substrates MG with Km and kcat of 1.43 ± 0.12 mM and 156.9 ± 5.5 min−1 respectively. The highest glyoxalase activity was found at 35–40°C and pH of 6.0–8.0, and the activity was significantly inhibited by Cu2+, Fe3+ and Zn2+. Mutagenesis studies based on our evaluation of conserved catalytic residues revealed that the Cys-185 and Glu-77 were essential for catalysis, whereas His-186 was less crucial for enzymatic function, although it participates in the catalytic process. The stationary-phase Escherichia coli cells became more susceptible to MG when hchA was deleted, which was complemented by an expression of plasmid-encoded hchA. Furthermore, an accumulation of intracellular MG was observed in hchA-deficient strains.