Elsinghorst E A, Mortlock R P
Department of Microbiology, Cornell University, Ithaca, New York 14853.
J Bacteriol. 1988 Dec;170(12):5423-32. doi: 10.1128/jb.170.12.5423-5432.1988.
D-Arabinose is degraded by Escherichia coli B via some of the L-fucose pathway enzymes and a D-ribulokinase which is distinct from the L-fuculokinase of the L-fucose pathway. We found that L-fucose and D-arabinose acted as the apparent inducers of the enzymes needed for their degradation. These enzymes, including D-ribulokinase, appeared to be coordinately regulated, and mutants which constitutively synthesized the L-fucose enzymes also constitutively synthesized D-ribulokinase. In contrast to D-arabinose-positive mutants of E. coli K-12, in which L-fuculose-1-phosphate and D-ribulose-1-phosphate act as inducers of the L-fucose pathway, we found that these intermediates did not act as inducers in E. coli B. To further characterize the E. coli B system, some of the L-fucose-D-arabinose genes were mapped by using bacteriophage P1 transduction. A transposon Tn10 insertion near the E. coli B L-fucose regulon was used in two- and three-factor reciprocal crosses. The gene encoding D-ribulokinase, designated darK, was found to map within the L-fucose regulon, and the partial gene order was found to be Tn10-fucA-darK-fucI-fucK-thyA.
大肠杆菌B通过一些L-岩藻糖途径的酶和一种与L-岩藻糖途径的L-岩藻糖激酶不同的D-核糖激酶来降解D-阿拉伯糖。我们发现L-岩藻糖和D-阿拉伯糖作为其降解所需酶的明显诱导物。这些酶，包括D-核糖激酶，似乎是协同调控的，组成型合成L-岩藻糖酶的突变体也组成型合成D-核糖激酶。与大肠杆菌K-12的D-阿拉伯糖阳性突变体不同，在后者中L-岩藻酮糖-1-磷酸和D-核糖酮糖-1-磷酸作为L-岩藻糖途径的诱导物，我们发现这些中间产物在大肠杆菌B中不起诱导作用。为了进一步表征大肠杆菌B系统，利用噬菌体P1转导对一些L-岩藻糖-D-阿拉伯糖基因进行了定位。在大肠杆菌B的L-岩藻糖调节子附近的一个转座子Tn10插入用于双因子和三因子互交。发现编码D-核糖激酶的基因（命名为darK）定位于L-岩藻糖调节子内，部分基因顺序为Tn10-fucA-darK-fucI-fucK-thyA。
