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The lactose operon from Lactobacillus casei is involved in the transport and metabolism of the human milk oligosaccharide core-2 N-acetyllactosamine.

ABSTRACT: The lactose operon (lacTEGF) from Lactobacillus casei strain BL23 has been previously studied. The lacT gene codes for a transcriptional antiterminator, lacE and lacF for the lactose-specific phosphoenolpyruvate: phosphotransferase system (PTSLac) EIICB and EIIA domains, respectively, and lacG for the phospho-?-galactosidase. In this work, we have shown that L. casei is able to metabolize N-acetyllactosamine (LacNAc), a disaccharide present at human milk and intestinal mucosa. The mutant strains BL153 (lacE) and BL155 (lacF) were defective in LacNAc utilization, indicating that the EIICB and EIIA of the PTSLac are involved in the uptake of LacNAc in addition to lactose. Inactivation of lacG abolishes the growth of L. casei in both disaccharides and analysis of LacG activity showed a high selectivity toward phosphorylated compounds, suggesting that LacG is necessary for the hydrolysis of the intracellular phosphorylated lactose and LacNAc. L. casei (lacAB) strain deficient in galactose-6P isomerase showed a growth rate in lactose (0.0293?±?0.0014?h-1) and in LacNAc (0.0307?±?0.0009?h-1) significantly lower than the wild-type (0.1010?±?0.0006?h-1 and 0.0522?±?0.0005?h-1, respectively), indicating that their galactose moiety is catabolized through the tagatose-6P pathway. Transcriptional analysis showed induction levels of the lac genes ranged from 130 to 320-fold in LacNAc and from 100 to 200-fold in lactose, compared to cells growing in glucose.

SUBMITTER: Bidart GN

PROVIDER: S-EPMC5940811 | biostudies-literature | 2018 May

REPOSITORIES: biostudies-literature

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The lactose operon from Lactobacillus casei is involved in the transport and metabolism of the human milk oligosaccharide core-2 N-acetyllactosamine.

Bidart Gonzalo N GN Rodríguez-Díaz Jesús J Pérez-Martínez Gaspar G Yebra María J MJ

Scientific reports 20180508 1

The lactose operon (lacTEGF) from Lactobacillus casei strain BL23 has been previously studied. The lacT gene codes for a transcriptional antiterminator, lacE and lacF for the lactose-specific phosphoenolpyruvate: phosphotransferase system (PTS<sup>Lac</sup>) EIICB and EIIA domains, respectively, and lacG for the phospho-β-galactosidase. In this work, we have shown that L. casei is able to metabolize N-acetyllactosamine (LacNAc), a disaccharide present at human milk and intestinal mucosa. The mut ...[more]

PMID: 29740087

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Project description:Genes encoding L-sorbose metabolism of Lactobacillus casei ATCC 393 have been identified on a 6.8-kb chromosomal DNA fragment. Sequence analysis revealed seven complete genes and a partial open reading frame transcribed as two units. The deduced amino acid sequences of the first transcriptional unit (sorRE) showed high similarity to the transcriptional regulator and the L-sorbose-1-phosphate reductase of the sorbose (sor) operon from Klebsiella pneumoniae. The other genes are transcribed as one unit (sorFABCDG) in opposite direction to sorRE. The deduced peptide sequence of sorF showed homology with the D-sorbitol-6-phosphate dehydrogenase encoded in the sor operon from K. pneumoniae and sorABCD to components of the mannose phosphotransferase system (PTS) family but especially to domains EIIA, EIIB, EIIC and EIID of the phosphoenolpyruvate-dependent L-sorbose PTS from K. pneumoniae. Finally, the deduced amino acid sequence of a truncated gene (sorG) located downstream of sorD presented high similarity with ketose-1,6-bisphosphate aldolases. Results of studies on enzyme activities and transcriptional analysis revealed that the two gene clusters, sorRE and sorFABCDG, are induced by L-sorbose and subject to catabolite repression by D-glucose. Data indicating that the catabolite repression is mediated by components of the PTS elements and by CcpA, are presented. Results of sugar uptake assays in L. casei wild-type and sorBC mutant strains indicated that L-sorbose is taken up by L-sorbose-specific enzyme II and that L. casei contains an inducible D-fructose-specific PTS. Results of growth analysis of those strains and a man sorBC double mutant suggested that L-sorbose is probably also transported by the D-mannose PTS. We also present evidence, from studies on a sorR mutant, suggesting that the sorR gene encodes a positive regulator of the two sor operons. Sequence alignment of SorR, SorC (K. pneumoniae), and DeoR (Bacillus subtilis) revealed that they might constitute a new group of transcriptional regulators.

Dataset Information

The lactose operon from Lactobacillus casei is involved in the transport and metabolism of the human milk oligosaccharide core-2 N-acetyllactosamine.

Publications

The lactose operon from Lactobacillus casei is involved in the transport and metabolism of the human milk oligosaccharide core-2 N-acetyllactosamine.

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