Clark B, Holms W H
J Gen Microbiol. 1976 Aug;96(2):191-201. doi: 10.1099/00221287-95-2-191.
In Escherichia coli (ATCCI5224; ML308), glucose and fructose phosphotransferase systems (PT-systems) are constitutive but activities are increased five and 10-fold respectively by aerobic growth on their respective substrates in defined media. In mixtures, glucose is used preferentially and the fructose PT-system activity is kept at its minimum; but, on glucose exhaustion, it overshoots its steady-state level and growth continues on fructose without lag. Cyclic AMP prevents overshoot. Continuous cultures operating as turbidostats on mixtures of glucose and fructose do not use fructose if sufficient glucose is present to support growth. If less glucose is available, it is all used and sufficient fructose is metabolized concurrently to maintain the growth rate characteristic of glucose. Both PT-systems are inhibited by hexose phosphates. Presence of homologous substrate specifically sensitizes each PT-system to inactivation by N-ethylmaleimide (NEM). Glucose diminishes the ability of fructose to sensitize its PT-system to NEM. This effect parallels the inhibition of fructose utilization by glucose and suggests that glucose denies fructose access to the fructose-specific part of the PT-system.
在大肠杆菌（ATCCI5224；ML308）中，葡萄糖和果糖磷酸转移酶系统（PT系统）是组成型的，但在限定培养基中，在各自底物上进行有氧生长时，其活性分别增加5倍和10倍。在混合物中，优先利用葡萄糖，果糖PT系统的活性保持在最低水平；但是，当葡萄糖耗尽时，其活性超过稳态水平，并且在果糖上继续生长而无延迟。环磷酸腺苷可防止活性过冲。在葡萄糖和果糖混合物上作为恒浊器运行的连续培养物，如果有足够的葡萄糖支持生长，则不会利用果糖。如果可利用的葡萄糖较少，则会全部被利用，同时会代谢足够的果糖以维持葡萄糖特有的生长速率。两种PT系统均受己糖磷酸抑制。同源底物的存在会使每个PT系统对N-乙基马来酰亚胺（NEM）的失活作用特别敏感。葡萄糖会降低果糖使其PT系统对NEM敏感的能力。这种效应与葡萄糖对果糖利用的抑制作用相似，表明葡萄糖阻止果糖进入PT系统中果糖特异性的部分。
