Adamowicz M, Conway T, Nickerson K W
School of Biological Sciences, University of Nebraska, Lincoln 68588.
Appl Environ Microbiol. 1991 Jul;57(7):2012-5. doi: 10.1128/aem.57.7.2012-2015.1991.
Two glucose-negative Escherichia coli mutants (ZSC113 and DF214) were unable to grow on glucose as the sole carbon source unless supplemented with pyrroloquinoline quinone (PQQ). PQQ is the cofactor for the periplasmic enzyme glucose dehydrogenase, which converts glucose to gluconate. Aerobically, E. coli ZSC113 grew on glucose plus PQQ with a generation time of 65 min, a generation time about the same as that for wild-type E. coli in a defined glucose-salts medium. Thus, for E. coli ZSC113 the Enter-Doudoroff pathway was fully able to replace the Embden-Meyerhof-Parnas pathway. In the presence of 5% sodium dodecyl sulfate, PQQ no longer acted as a growth factor. Sodium dodecyl sulfate inhibited the formation of gluconate from glucose but not gluconate metabolism. Adaptation to PQQ-dependent growth exhibited long lag periods, except under low-phosphate conditions, in which the PhoE porin would be expressed. We suggest that E. coli has maintained the apoenzyme for glucose dehydrogenase and the Entner-Doudoroff pathway as adaptations to an aerobic, low-phosphate, and low-detergent aquatic environment.
两个葡萄糖阴性大肠杆菌突变体（ZSC113和DF214）在以葡萄糖作为唯一碳源时无法生长，除非添加吡咯喹啉醌（PQQ）。PQQ是周质酶葡萄糖脱氢酶的辅因子，该酶将葡萄糖转化为葡萄糖酸盐。在有氧条件下，大肠杆菌ZSC113在葡萄糖加PQQ的培养基上生长，代时为65分钟，与野生型大肠杆菌在限定的葡萄糖盐培养基中的代时大致相同。因此，对于大肠杆菌ZSC113来说，Entner-Doudoroff途径完全能够替代Embden-Meyerhof-Parnas途径。在5%十二烷基硫酸钠存在的情况下，PQQ不再作为生长因子起作用。十二烷基硫酸钠抑制了由葡萄糖形成葡萄糖酸盐，但不抑制葡萄糖酸盐的代谢。适应PQQ依赖型生长表现出较长的延迟期，低磷酸盐条件除外，在低磷酸盐条件下PhoE孔蛋白会表达。我们认为，大肠杆菌保留了葡萄糖脱氢酶的脱辅基酶和Entner-Doudoroff途径，作为对有氧、低磷酸盐和低洗涤剂水生环境的适应。
