Galactoside

About: Galactoside is a research topic. Over the lifetime, 662 publications have been published within this topic receiving 15406 citations. The topic is also known as: galactosides.

Proton-coupled accumulation of galactoside in Streptococcus lactis 7962.

Abstract: When cells of the anaerobe Streptococcus lactis 7962 are deprived of their normal fermentable energy source, active transport of galactosides is completely abolished although the membrane carriers are still capable of facilitating the equilibration of sugars across the cell membrane. In these nonmetabolizing cells it was possible to test the Mitchell hypothesis of obligatory coupling of proton movement with sugar transport. This hypothesis was supported by alkalinization of the medium observed when thiomethylgalactoside was added to a lightly buffered suspension of S. lactis cells. Conversely, addition of protons resulted in active transport of thiomethylgalactoside. Accumulation of thiomethylgalactoside to a concentration more than 20-times that in the external medium was induced by suddenly exposing cells to a medium at pH 6; no accumulation of thiomethylgalactoside was observed with cells exposed to pH 8.Active transport of thiomethylgalactoside occurred in the absence of energy metabolism when S. lactis cells were treated with valinomycin. This ionophore allowed intracellular K(+) to flow out, thus imposing a membrane potential (inside negative). This potential resulted in a proton uptake and an associated active transport of galactoside. The membrane potential was measured from the distribution ratio (inside/outside) of K(+) in the presence of valinomycin. The pH gradient was measured from the distribution ratio of [(14)C]methylamine. The protonmotive force, calculated from the membrane potential and the pH gradient, was found to be directly related to the accumulation of galactoside, in accordance with the chemiosmotic hypothesis.

Combined use of β-galactosidase and sialyltransferase coupled with in situ regeneration of CMP-sialic acid for one pot synthesis of oligosaccharides

Abstract: A single reaction vessel process for the synthesis of a sialylated galactoside is disclosed. The synthesis utilizes a β-galactosidase to catalyze the reaction of a galactose-containing substrate and an acceptor to form a new galactosyl glycoside that is then sialylated using a cyclic multienzyme synthesis system to form CMP-sialic acid that sialylates the formed galactosyl glycoside in the presence of an α-sialyltransferase. The value of Km /Vmax for the formed galactosyl glycoside as a substrate for the α-sialyltransferase is less than one-third the Km /Vmax value for the galactose-containing substrate for that α-sialyltransferase.

PHYSIOLOGY OF THE INHIBITION BY GLUCOSE OF THE INDUCED SYNTHESIS OF THE β-GALACTOSIDE-ENZYME SYSTEM OF ESCHERICHIA COLI

Abstract: In previous papers a model (Cohn, 1956, 1958; Cohn and Horibata, 1959a, b) was described which completely rationalized the kinetics of the induction by galactosides and the inhibition by glucose in terms of the properties of the galactoside-permease. However, little information was provided on the mechanism by which glucose acts as an inhibitor of induction. It is known (Cohn and Horibata, 1959a, b; Herzenberg, 1958) that glucose inhibits induced f-galactosidase synthesis in mutants which lack permease, and, conversely, induced permease synthesis is inhibited in mutants which lack f3-galactosidase. Therefore, it is clear that the inhibiting action of glucose is not at the level of the activity of either permease or galactosidase but at some other point in the series of reactions leading to the synthesis of either component. The experiments described here are best understood in terms of the hypothesis that induced enzymes are those whose synthesis can be repressed (Neidhardt and Magasanik, 1956a, b; 1957; Vogel, 1957) by some derivative of the carbon source. The inducer relieves the repression. Certain very inhibitory carbohydrates, such as glucose or mannitol, are metabolized to yield high internal levels of repressor, whereas less inhibitory substances such as succinate and lactate give lower levels of repressor. The repressor-hypothesis with some qualifications will be used as the basis for the description of the data.

Amino acid sequence and molecular characterization of a D-galactoside-specific lectin purified from sea urchin (Anthocidaris crassispina) eggs.

Abstract: The complete amino acid sequence of a 11.5-kDa subunit of D-galactoside binding lectin purified from sea urchin (Anthocidaris crassispina) eggs is presented. The 105-residue sequence of the subunit was determined by analysis of the intact S-carbamoylmethylated protein and peptides generated by digestion with Achromobacter protease I or Staphylococcus aureus V8 protease. The lectin exists as a disulfide-linked homodimer of two subunits; the dimeric form is essential for hemagglutination activity. However, the monomeric form obtained by partial reduction retains the carbohydrate binding capacity. Neither Ca2+ nor SH reagent is essential for hemagglutination or carbohydrate binding. The sequence has no similarity to that of any known protein and apparently represents a new type of galactoside binding lectin.