Kitaoka Motomitsu, Tian Jiesheng, Nishimoto Mamoru
National Food Research Institute, 2-1-12 Kannondai, Tsukuba, Ibaraki 305-8642, Japan.
Appl Environ Microbiol. 2005 Jun;71(6):3158-62. doi: 10.1128/AEM.71.6.3158-3162.2005.
A lacto-N-biose phosphorylase (LNBP) was purified from the cell extract of Bifidobacterium bifidum. Its N-terminal and internal amino acid sequences were homologous with those of the hypothetical protein of Bifidobacterium longum NCC2705 encoded by the BL1641 gene. The homologous gene of the type strain B. longum JCM1217, lnpA, was expressed in Escherichia coli to confirm that it encoded LNBP. No significant identity was found with any proteins with known function, indicating that LNBP should be classified in a new family. The lnpA gene is located in a novel putative operon for galactose metabolism that does not contain a galactokinase gene. The operon seems to be involved in intestinal colonization by bifidobacteria mediated by metabolism of mucin sugars. In addition, it may also resolve the question of the nature of the bifidus factor in human milk as the lacto-N-biose structure found in milk oligosaccharides.
从两歧双歧杆菌的细胞提取物中纯化出一种乳糖 - N - 二糖磷酸化酶（LNBP）。其N端和内部氨基酸序列与长双歧杆菌NCC2705中由BL1641基因编码的假定蛋白的氨基酸序列同源。长双歧杆菌模式菌株JCM1217的同源基因lnpA在大肠杆菌中表达，以证实其编码LNBP。未发现与任何已知功能的蛋白质有显著同源性，这表明LNBP应归类于一个新的家族。lnpA基因位于一个新的假定的半乳糖代谢操纵子中，该操纵子不包含半乳糖激酶基因。该操纵子似乎参与了由粘蛋白糖代谢介导的双歧杆菌在肠道的定殖。此外，它还可能解决人乳中双歧因子的性质问题，因为在乳寡糖中发现了乳糖 - N - 二糖结构。
