Regulation Of Sugar Transport And Metabolism In Oral Bacteria

对干酪乳杆菌ATCC 334的基因组序列进行了检测，发现了两个操纵子，它们可能异化蔗糖的五个异构体。为了验证这一假设，干酪乳杆菌ATCC 334的细胞在添加了各种糖的特定培养基中生长，包括五种异构体二糖中的每一种。从生长在蔗糖异构体上的细胞制备的提取物含有两种高水平的多肽，MRS分别为50,000和17,500。在以葡萄糖、麦芽糖或蔗糖生长的细胞中，这两种蛋白质都不存在。蛋白质组学、酶学和Western印迹分析表明，该50 kDa蛋白是一种依赖于NAD+和金属离子的磷酸-α-葡萄糖苷酶。对该低聚体酶进行了纯化，并提出了催化机理。较小的多肽代表磷酸烯醇式丙酮酸依赖的糖磷酸转移酶系统的EIIA组分。 磷酸-α-葡萄糖苷酶和EIIA分别由LSEI_0369(SIMA)和LSEI_0374(SIMF)基因编码，共7个基因组成蔗糖异构体代谢(SIM)操纵子。Northern印迹分析表明，干酪乳杆菌ATCC 334在蔗糖异构体上的对数生长过程中，有3个转录本表达上调。SIMA和SIMF基因的内部探针分别与1.5和1.3 kb的转录本杂交。两种探针均检测到6.8kb的mRNA转录，这表明整个sim操纵子是共转录的。 这项研究的结果已经发表在同行评议的《细菌学杂志》上

Inspection of the genome sequence of Lactobacillus casei ATCC 334 revealed two operons that might dissimilate the five isomers of sucrose. To test this hypothesis, cells of L. casei ATCC 334 were grown in a defined medium supplemented with various sugars, including each of the five isomeric disaccharides. Extracts prepared from cells grown on the sucrose isomers contained high levels of two polypeptides with Mrs of 50,000 and 17,500. Neither protein was present in cells grown on glucose, maltose or sucrose. Proteomic, enzymatic, and Western blot analyses identified the 50-kDa protein as an NAD+ and metal ion-dependent phospho-alpha-glucosidase. The oligomeric enzyme was purified, and a catalytic mechanism is proposed. The smaller polypeptide represented an EIIA component of the phosphoenolpyruvate-dependent sugar phosphotransferase system. Phospho-alpha-glucosidase and EIIA are encoded by genes at the LSEI_0369 (simA) and LSEI_0374 (simF) loci, respectively, in a block of seven genes comprising the sucrose isomer metabolism (sim) operon. Northern blot analyses provided evidence that three mRNA transcripts were up-regulated during logarithmic growth of L. casei ATCC 334 on sucrose isomers. Internal simA and simF gene probes hybridized to 1.5- and 1.3-kb transcripts, respectively. A 6.8-kb mRNA transcript was detected by both probes, which was indicative of cotranscription of the entire sim operon. The results of this study have been published in the peer reviewed Journal of Bacteriology