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Cold-adapted β-galactosidase from the Antarctic psychrophile Pseudoalteromonas haloplanktis
Hoyoux, A.; Jennes, I.; Dubois, P.; Genicot, S.; Dubail, F.; François, J.-M.; Baise, E.; Feller, G.; Gerday, C. (2001). Cold-adapted β-galactosidase from the Antarctic psychrophile Pseudoalteromonas haloplanktis. Appl. Environ. Microbiol. 67(4): 1529-1535. dx.doi.org/10.1128/AEM.67.4.1529-1535.2001
In: Applied and Environmental Microbiology. American Society for Microbiology: Washington. ISSN 0099-2240; e-ISSN 1098-5336, meer
Peer reviewed article  
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  • Hoyoux, A.
  • Jennes, I.
  • Dubois, P., meer
  • Genicot, S.
  • Dubail, F.
  • François, J.-M.
  • Baise, E.
  • Feller, G., meer
  • Gerday, C., meer
Abstract
    The β-galactosidase from the Antarctic gram-negative bacterium Pseudoalteromonas haloplanktis TAE 79 was purified to homogeneity. The nucleotide sequence and the NH2-terminal amino acid sequence of the purified enzyme indicate that the β-galactosidase subunit is composed of 1,038 amino acids with a calculated M r of 118,068. This β-galactosidase shares structural properties with Escherichia coli β-galactosidase (comparable subunit mass, 51% amino sequence identity, conservation of amino acid residues involved in catalysis, similar optimal pH value, and requirement for divalent metal ions) but is characterized by a higher catalytic efficiency on synthetic and natural substrates and by a shift of apparent optimum activity toward low temperatures and lower thermal stability. The enzyme also differs by a higher pI (7.8) and by specific thermodynamic activation parameters. P. haloplanktis β-galactosidase was expressed in E. coli, and the recombinant enzyme displays properties identical to those of the wild-type enzyme. Heat-induced unfolding monitored by intrinsic fluorescence spectroscopy showed lower melting point values for both P. haloplanktiswild-type and recombinant β-galactosidase compared to the mesophilic enzyme. Assays of lactose hydrolysis in milk demonstrate that P. haloplanktis β-galactosidase can outperform the current commercial β-galactosidase from Kluyveromyces marxianusvar. lactis, suggesting that the cold-adapted β-galactosidase could be used to hydrolyze lactose in dairy products processed in refrigerated plants.
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