CO-INDUCTION OF BETA-GALACTOSIDASE AND LACTOSE-P-ENOLPYRUVATE PHOSPHOTRANSFERASE SYSTEM IN STREPTOCOCCUS-SALIVARIUS AND STREPTOCOCCUS-MUTANS
CO-INDUCTION OF BETA-GALACTOSIDASE AND LACTOSE-P-ENOLPYRUVATE PHOSPHOTRANSFERASE SYSTEM IN STREPTOCOCCUS-SALIVARIUS AND STREPTOCOCCUS-MUTANS
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DOI：
10.1128/jb.136.3.900-908.1978
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发表时间：
1978-01-01
影响因子：
3.2
通讯作者：
LO, GCY
中科院分区：
文献类型：
--
作者：
HAMILTON, IR;LO, GCY
添加乳糖、半乳糖或异丙基。将- d -硫代半乳糖苷（IPTG）作用于唾液链球菌25975的葡萄糖培养细胞，导致乳糖- p[磷酸]-烯醇丙酮酸磷酸转移酶系统（乳糖- pts）和。半乳糖苷酶，后者是主要的代谢系统。在变形链球菌和血链球菌10556的不同菌株中，乳糖- pts是主要的代谢途径。-半乳糖苷酶诱导到低或可忽略的水平。在所有情况下，乳糖- pts的诱导导致6-P- β -半乳糖苷酶的同时诱导。乳糖诱导乳糖- pts和。β。所有菌株的-半乳糖苷酶均被葡萄糖和其他分解代谢物（尤其是果糖）抑制。诱导。唾液链球菌25975中-半乳糖苷酶对葡萄糖抑制具有相对抗性。IPTG和乳糖诱导实验表明，乳糖代谢的细胞代谢物是酶活性的抑制物。外源性c[环]AMP逆转了葡萄糖对β的短暂抑制。在接受乳糖的唾液链球菌25975细胞中诱导-半乳糖苷酶，条件是细胞在少量甲苯中生长以克服对该核苷酸的渗透屏障。cAMP无法克服β的永久抑制。-半乳糖苷酶活性在这些条件下显著降低。
The addition of lactose, galactose, or isopropyl-.beta.-D-thiogalactoside (IPTG) to glucose-grown cells of S. salivarius 25975 resulted in the co-induction of both the lactose-P[phospho]-enolpyruvate phosphotransferase system (lactose-PTS) and .beta.-galactosidase, with the latter the predominant metabolic system. With various strains of S. mutans and S. sanguis 10556, the lactose-PTS was the major metabolic pathway with .beta.-galactosidase induced either to low or negligible levels. In all cases, induction of the lactose-PTS resulted in the concomitant induction of 6-P-.beta.-galactosidase. The induction by lactose of both the lactose-PTS and .beta.-galactosidase in all strains was repressed by glucose and other catabolites, notably, fructose. Induction of .beta.-galactosidase in S. salivarius 25975 by IPTG was relatively resistant to glucose repression. Induction experiments with IPTG and lactose suggested that a cellular metabolite of lactose metabolism was a repressor of enzyme activity. Exogenous c[cyclic]AMP reversed the transient repression by glucose of .beta.-galactosidase induction in cells of S. salivarius 25975 receiving lactose, provided the cells were grown with small amounts of toluene to overcome the permeability barrier to this nucleotide. cAMP was unable to overcome the permanent repression of .beta.-galactosidase activity to a significant extent under these conditions.