Characterization and immobilization of a novel SGNH hydrolase (Est24) from Sinorhizobium meliloti

Appl Microbiol Biotechnol. 2013 Feb;97(4):1637-47. doi: 10.1007/s00253-012-4038-8. Epub 2012 Apr 13.

Abstract

A novel oligomeric SGNH hydrolase (Est24) from Sinorhizobium meliloti was identified, actively expressed in Escherichia coli, characterized, and immobilized for industrial application. Sequence analysis of Est24 revealed a putative catalytic triad (Ser¹³-Asp¹⁶³-His¹⁶⁹), with moderate homology to other SGNH hydrolases. Est24 was more active toward short-chain esters, such as p-nitrophenyl acetate, butyrate, and valerate, while the S13A mutant completely lost its activity. Moreover, the activity of Est24 toward α- and β-naphthyl acetate, and enantioselectivity on (R)- and (S)-methyl-3-hydroxy-2-methylpropionate were tested. Est24 exhibited optimum activity at mesophilic temperature ranges (45-55 °C), and slightly alkaline pH (8.0). Structural and mutagenesis studies revealed critical residues involved in the formation of a catalytic triad and substrate-binding pocket. Cross-linked enzyme aggregates (CLEAs) of Est24 with and without amyloid fibrils were prepared, and amyloid fibril-linked Est24 with amyloid fibrils retained 83 % of its initial activity after 1 h of incubation at 60 °C. The high thermal stability of immobilized Est24 highlights its potential in the pharmaceutical and chemical industries.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Bacterial Proteins / chemistry*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Enzyme Stability
  • Enzymes, Immobilized / chemistry
  • Enzymes, Immobilized / genetics
  • Enzymes, Immobilized / metabolism
  • Hydrolases / chemistry*
  • Hydrolases / genetics
  • Hydrolases / metabolism*
  • Kinetics
  • Models, Molecular
  • Molecular Sequence Data
  • Phylogeny
  • Sequence Alignment
  • Sinorhizobium meliloti / chemistry
  • Sinorhizobium meliloti / enzymology*
  • Sinorhizobium meliloti / genetics
  • Substrate Specificity

Substances

  • Bacterial Proteins
  • Enzymes, Immobilized
  • Hydrolases