Regulation of lactose-phosphoenolpyruvate-dependent phosphotransferase system and beta-D-phosphogalactoside galactohydrolase activities in Lactobacillus casei.
AUTOR(ES)
Chassy, B M
RESUMO
The lactose-phosphoenolpyruvate-dependent phosphotransferase system (lac-PTS) and beta-D-phosphogalactoside galactohydrolase (P-beta-gal) mediate the metabolism of lactose by Lactobacillus casei. Starved cells of L. casei contained a high intracellular concentration of phosphoenolpyruvate, and this endogenous energy reserve facilitated characterization of phosphotransferase system activities in physiologically intact cells. Data obtained from transport studies with whole cells and from in vitro phosphotransferase system assays with permeabilized cells revealed that the lac-PTS had a high affinity for beta-galactosides (e.g., lactose, lactulose, lactobionic acid, and arabinosyl-beta-D-galactoside). lac-PTS and P-beta-gal activities were determined in wild-type strains and strains defective in the glucose-phosphoenolpyruvate-dependent phosphotransferase system after growth on various sugars and in the presence of potential inducers. We found that (i) the lac genes (i.e., the genes coding for the lac-PTS proteins and P-beta-gal) were induced by metabolizable and non-metabolizable beta-galactosides (presumably acting as their phosphorylated derivatives), (ii) galactose 6-phosphate was not an inducer in most strains, (iii) the ratio of lac-PTS activity to P-beta-gal activity in a given strain was not constant, and (iv) inhibition of lac gene expression during growth on glucose was a consequence of glucose-phosphoenolpyruvate-dependent phosphotransferase system-mediated inducer exclusion, repressive effects of a functional glucose-phosphoenolpyruvate-dependent phosphotransferase system and glucose-derived metabolites. The expression of the lac-PTS structural genes and the expression of the P-beta-gal gene are independently regulated and may be subject to both positive control and negative control.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=217591Documentos Relacionados
- Cloning and expression of the beta-D-phosphogalactoside galactohydrolase gene of Lactobacillus casei in Escherichia coli K-12.
- Regulation and characterization of the galactose-phosphoenolpyruvate-dependent phosphotransferase system in Lactobacillus casei.
- Transport of d-Xylose in Lactobacillus pentosus, Lactobacillus casei, and Lactobacillus plantarum: Evidence for a Mechanism of Facilitated Diffusion via the Phosphoenolpyruvate:Mannose Phosphotransferase System
- Pentitol metabolism in Lactobacillus casei.
- Role of the phosphoenolpyruvate-dependent glucose phosphotransferase system of Streptococcus mutans GS5 in the regulation of lactose uptake.