Cold-adapted β-galactosidase from the Antarctic psychrophile Pseudoalteromonas haloplanktis

被引:133
作者
Hoyoux, A [1 ]
Jennes, I [1 ]
Dubois, P [1 ]
Genicot, S [1 ]
Dubail, F [1 ]
François, JM [1 ]
Baise, E [1 ]
Feller, G [1 ]
Gerday, C [1 ]
机构
[1] Univ Liege, Inst Chem, Biochem Lab, B-4000 Liege, Belgium
关键词
D O I
10.1128/AEM.67.4.1529-1535.2001
中图分类号
Q81 [生物工程学(生物技术)]; Q93 [微生物学];
学科分类号
071005 ; 0836 ; 090102 ; 100705 ;
摘要
The beta -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 beta -galactosidase subunit is composed of 1,038 amino acids with a calculated M, of 118,068. This beta -galactosidase shares structural properties with Escherichia coli beta -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 beta -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. haloplanktis wild-type and recombinant beta -galactosidase compared to the mesophilic enzyme. Assays of lactose hydrolysis in milk demonstrate that P. haloplanktis beta -galactosidase can outperform the current commercial beta -galactosidase from Kluyveromyces marxianus var. lactis, suggesting that the cold-adapted beta -galactosidase could be used to hydrolyze lactose in dairy products processed in refrigerated plants.
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页码:1529 / 1535
页数:7
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