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

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Distinct roles of β-galactosidase paralogues of the rumen bacterium Mannheimia succiniciproducens
Eun Gyeong Lee; Seonghun KimDoo-Byoung Oh; S Y Lee; Oh Suk Kwon
Bibliographic Citation
Journal of Bacteriology, vol. 194, no. 2, pp. 426-436
Publication Year
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.
Amer Soc Microb
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Jeonbuk Branch Institute > Microbial Biotechnology Research Center > 1. Journal Articles
Aging Convergence Research Center > 1. Journal Articles
Division of Bio Technology Innovation > SME Support Center > 1. Journal Articles
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