Showing papers on "Melibiose published in 1978"

Cation-Sugar Cotransport in the Melibiose Transport System of Escherichia coli

Abstract: The entry of Na+ or H+ into cells of Escherichia coli via the melibiose transport system was stimulated by the addition of certain galactosides. The principal cell used in these studies (W3133) was a lactose transport negative strain of E. coli possessing an inducible melibiose transport system. Such cells were grown in the presence of melibiose, washed, and incubated in the presence of 25 μM Na+. The addition of thiomethylgalactoside (TMG) resulted in a fall in Na+ concentration in the incubation medium. No TMG-stimulated Na+ movement was observed in uninduced cells. In an α-galactosidase negative derivative of W3133 (RA11) a sugar-stimulated Na+ uptake was observed in meliboise-induced cells on the addition of melibiose, thiodigalactoside, methyl-α-galactoside, methyl-β-galactoside, and galactose, but not lactose. It was inferred from these studies that the substrates of the melibiose system enter the cell on the melibiose carrier associated with the simultaneous entry of Na+ when this cation is present...

Role of Na+ and Li+ in thiomethylgalactoside transport by the melibiose transport system of Escherichia coli.

Abstract: Thiomethyl-beta-galactoside (TMG) accumulation via the melibiose transport system was studied in lactose transport-negative strains of Escherichia coli. TMG uptake by either intact cells or membrane vesicles was markedly stimulated by Na+ or Li+ between pH 5.5 and 8. The Km for uptake of TMG was approximately 0.2 mM at an external Na+ concentration of 5 mM (pH 7). The alpha-galactosides, melibiose, methyl-alpha-galactoside, and o-nitrophenyl-alpha-galactoside had a high affinity for this system whereas lactose, maltose and glucose had none. Evidence is presented for Li+-TMG or Na+-TMG cotransport.

Effect of lithium ion on melibiose transport in Escherichia coli.

Abstract: Both Li+ and Na+ stimulated the uptake of thiomethylgalactoside by the melibiose transport system ofEscherichia coli. On the other hand, Li+ inhibited the growth of cells on melibiose as a sole source of carbon. This inhibition was specific for melibiose, and Li+ had no effect on growth of cells on glucose, galactose, lactose, or glycerol. The effect of the cation on melibiose transport was investigated in a mutant which cannot utilize glucose. After entry into this cell, melibiose is cleaved into glucose and galactose by α-galactosidase, and the resulting glucose is excreted. Since the entry step was found to be rate-limiting, glucose production could be taken as a measure of melibiose transport. Li+ inhibited the transport of melibiose, but not the induction of the melibiose operon nor the activity of α-galactosidase. Li+ was found to inhibit the entry ofp-nitrophenyl-α-d-galactoside, but notp-nitrophenyl-β-d-galactoside entry. Thus, the cation specificity for the melibiose membrane carrier varies with different transport substrates.

Permease-specific mutations in Salmonella typhimurium and Escherichia coli that release the glycerol, maltose, melibiose, and lactose transport systems from regulation by the phosphoenolpyruvate:sugar phosphotransferase system.

Abstract: Several carbohydrate permease systems in Salmonella typhimurium and Escherichia coli are sensitive to regulation by the phosphoenolpyruvate:sugar phosphotransferase system. Mutant Salmonella strains were isolated in which individual transport systems had been rendered insensitive to regulation by sugar substrates of the phosphotransferase system. In one such strain, glycerol uptake was insensitive to regulation; in another, the maltose transport system was resistant to inhibition; and in a third, the regulatory mutation specifically rendered the melibiose permease insensitive to regulation. An analogous mutation in E. coli abolished inhibition of the transport of beta-galactosides via the lactose permease system. The mutations were mapped near the genes which code for the affected transport proteins. The regulatory mutations rendered utilization of the particular carbohydrates resistant to inhibition and synthesis of the corresponding catabolic enzymes partially insensitive to repressive control by sugar substrates of the phosphotransferase system. Studies of repression of beta-galactosidase synthesis in E. coli were conducted with both lactose and isopropyl beta-thiogalactoside as exogenous sources of inducer. Employing high concentrations of isopropyl beta-thiogalactoside, repression of beta-galactosidase synthesis was not altered by the lactose-specific transport regulation-resistant mutation. By contrast, the more severe repression observed with lactose as the exogenous source of inducer was partially abolished by this regulatory mutation. The results support the conclusions that several transport systems, including the lactose permease system, are subject to allosteric regulation and that inhibition of inducer uptake is a primary cause of the repression of catabolic enzyme synthesis.

Production of α-galactosidase fromAspergillus awamori: Properties and action on para-nitrophenyl α-D-galactopyranoside and galacto-Oligosaccharides of soy milk

Abstract: Soybean products including soy milk can provide needed protein for human consumption. Soybean flour contains raffinose and stachyose considered responsible for flatulence often associated with soy products. A partially purified preparation of α-galactosidase and invertase, prepared fromAspergillus awamori NRRL 4869 cultured on wheat bran, hydrolyzes the oligosaccharides of soy milk. The α-galactosidase exhibited its maximum activity at pH 5.0 and was stable in that pH range. The optimum temperature was 50 C; however, 8% of α-galactosidase activity was lost after 15 min at 55 C., and complete inactivation was observed after 14 min at 70 C. Parachloromercuribenzoate, AgNO3, HgCl2, and iodine exhibited strong inhibitory effects on the enzymes. Km values of the α-galactosidase with melibiose and raffinose as substrates were 3.0 and 3.6 × 10−2 M, respectively, and the molecular weights of both enzymes were estimated to be about 130,000 on the basis of Sephadex and sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis.

Mechanism ofCoaggregation Between Actinomyces viscosus T14VandStreptococcus sanguis 34

Abstract: Actinomyces viscosus T14VandStreptococcus sanguis 34coaggregate bya mechanism whichisnotinhibited by1M NaCl, isdextran independent, requires calcium, ispH dependent withan optimumatpH 8.0to8.5, andappearsto require theinteraction ofa protein orglycoprotein on A.viscosus witha carbohydrate on S.sanguis. Thecoaggregation isinhibited more than80%by0.01M lactose, 0.02M /l-methyl-D-galactoside, or 0.05M D-galactose; inhibition of coaggregation was lessthan10%in0.1M a-methyl-D-galactoside, melibiose,

Lactobacilli isolated from French saucisson (taxonomic study).

Abstract: 190 Lactobacilli strains originating from saucisson produced in France, were isolated. The use of numerical taxonomy enabled 6 representative taxa to be established, defined by average biochemical profiles, differing greatly from those of Lactobacilli from dairy origins. Two groups of tests seem to be of particular interest in order to characterize these strains: 1. Fermentaion of ribose: positive, Arginine dihydrolase: positive, Gas production: negative. 2. Fermentation of melibiose: positive, Fermentation of raffinose: negative.

[Arabinose, melibiose and xylose oxidation and fermentation in "Serratia" (author's transl)].

Abstract: The oxidative and fermentative metabolisms of D(+)raffinose, D(-)arabinose, L(+)arabinose, D(+)melibiose and D(+)xylose were compared in 181 strains belonging to the genus Serratia, including collection strains and clinical isolates from various sources. At 30 degrees C, raffinose was neither fermented nor oxidized by S. marcescens, but was fermented by S. liquefaciens and S. rubidaea. D(-)arabinose was oxidized by all strains. L(+)arabinose, melibiose and xylose were fermented by all S. liquefaciens and S. rubidaea, while they were oxidized by most S. marcescens. Two strains of the latter species, however, were able to ferment xylose. The use of Hugh and Leifson's oxidation-fermentation medium containing melibiose or L(+)arabinose can help to differentiate S. rubidaea from pigmented strains of S. marcescens and to differentiate S. liquefaciens from unpigmented strains of S. marcescens.