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Title 

Distinct roles of β-galactosidase paralogues of the rumen bacterium Mannheimia succiniciproducens

Authors 

Eun Gyeong LeeSeonghun KimDoo-Byoung OhS Y LeeOh Suk Kwon

Publisher 

American Society for Microbiology

Issue Date 

2012

Citation 

Journal of Bacteriology, vol. 194, no. 2, pp. 426-436

Abstract 

Mannheimia succiniciproducens, a rumen bacterium belonging to the family Pasteurellaceae, has two putative β-galactosidase genes, bgaA and bgaB, encoding polypeptides whose deduced amino acid sequences share 56% identity with each other and show approximately 30% identity to the Escherichia coli gene for LacZ. The M. succiniciproducens bgaA (MsbgaA) gene-deletion mutant was not able to grow on lactose as the sole carbon source, suggesting its essential role in lactose metabolism, whereas the MsbgaB gene-deletion mutant did not show any growth defect on a lactose medium. Furthermore, the expression of the MsbgaA gene was induced by the addition of lactose in the growth medium, whereas the MsbgaB gene was constitutively expressed independently of a carbon source. Biochemical characterization of the recombinant proteins revealed that MsBgaA is more efficient than MsBgaB in hydrolyzing o-nitrophenyl-β-D-galactopyranoside and p-nitrophenyl-β-D-galactopyranoside. MsBgaA was highly specific for the hydrolysis of lactose, with a catalytic efficiency of 46.9 s -1mM -1. However, MsBgaB was more efficient for the hydrolysis of lactulose than lactose, and the catalytic efficiency was 10.0 s -1mM -1. Taken together, our results suggest that the β-galactosidase paralogues of M. succiniciproducens BgaA and BgaB play a critical role in lactose metabolism and in an unknown but likely specific function for rumen bacteria, respectively.

ISSN 

0021-9193

Link 

http://dx.doi.org/10.1128/JB.05911-11

Appears in Collections

1. Journal Articles > Journal Articles

Registered Date

2017-04-19


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