ヒトミルクオリゴ糖によるビフィズス菌増殖促進作用の分子機構

抄録

 Bifidobacteria rapidly colonize in the intestines of breast-fed infants after their births. Though human milk oligosaccharides (HMOs) were identified as the factor promoting intestinal growths of bifidobacteria 60 years ago, the molecular mechanism how bifidobacteria metabolize HMOs has not been clarified for long time. Discovery of the metabolic pathway specific to galacto-N-biose (GNB) and lacto-N-biose I (LNB) of bifidobacteria has led to reveal the mechanism, since components of HMOs often include the structure of LNB. Infant-type bifidobacterial species possess the GNB/LNB pathway. Extracellular enzymatic system liberating LNB from HMOs was identified from Bifidobacterium bifidum. On the other hand, Bifidobacterium longum subsp. infantis imports intact HMO to be hydrolyzed by intracellular enzymes, even though it possesses the GNB/LNB pathway. LNB is expected as potent bifidus factor for infant-type species. LNB was produced practically from sucrose and GlcNAc by using four bifidobacterial enzymes including enzymes constituting the GNB/LNB pathway.