Hsp31 of Escherichia coli K-12 is glyoxalase III.
Mol Microbiol
; 81(4): 926-36, 2011 Aug.
Article
em En
| MEDLINE
| ID: mdl-21696459
ABSTRACT
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 K(m) and k(cat) of 1.43±0.12 mM and 156.9±5.5 min⻹ 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 Cu²âº, Fe³âº and Zn²âº. 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.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Chaperonas Moleculares
/
Proteínas de Escherichia coli
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Escherichia coli K12
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Aldeído Oxirredutases
Idioma:
En
Ano de publicação:
2011
Tipo de documento:
Article