scispace - formally typeset
Search or ask a question
Topic

Melibiose

About: Melibiose is a research topic. Over the lifetime, 1002 publications have been published within this topic receiving 27300 citations. The topic is also known as: Melibiose.


Papers
More filters
Journal ArticleDOI
TL;DR: Two genes (agal1 and agal2) encoding α-galactosidases were identified by sequence-based screening approaches for high-temperature processes for the degradation of raffinose family oligosaccharides.
Abstract: Two genes (agal1 and agal2) encoding α-galactosidases were identified by sequence-based screening approaches. The gene agal1 was identified from a data set of a sequenced hot spring metagenome, and the deduced amino-acid sequence exhibited 99% identity to an α-galactosidase from the thermophilic bacterium Dictyoglomus thermophilum. The gene agal2 was identified from the whole genome sequence of the thermophile Meiothermus ruber. The amino-acid sequences exhibited structural motifs typical for glycoside hydrolase (GH) family 36 members and were also differentiated into different subgroups of this family. Recombinant production of the heat-active GH36b enzyme Agal1 (87 kDa) and GH36bt enzyme Agal2 (57 kDa) was carried out in E. coli. Agal1 exhibited a specific activity of 1502.3 U/mg at 80 °C, pH 6.5, and Agal2 225.4 U/mg at 60–70 °C, pH 6.5. Half-lives of 14 h (Agal1) and 39 h (Agal2) were obtained at 50 °C, and Agal1 showed half-lives of 4 and 2 h at 70 and 80 °C, respectively. In addition to the natural substrates melibiose, raffinose, and stachyose, 4NP α-d-galactopyranoside was hydrolyzed. Galactose was also liberated from locust bean gum. Both heat-active enzymes are attractive candidates for application in food and feed industry for high-temperature processes for the degradation of raffinose family oligosaccharides.

24 citations

Journal ArticleDOI
TL;DR: A comparison of SNA-III to the previously described elderberry-bark lectins indicated that the seed lectin is well distinct from them, being twice as potent as D-galactose, melibiose, and 2-amino-2-deoxy-D- Galactose.

24 citations

Journal ArticleDOI
TL;DR: Analysis of infrared polarized absorbance spectra and linear dichroism spectra of reconstituted melibiose permease from Escherichia coli shows that the oriented structures correspond mainly to tilted transmembrane alpha-helices, forming an average angle of approximately 26 degrees with the membrane normal in substrate-free medium.

24 citations

Journal ArticleDOI
TL;DR: The Na+ coupling in MelBSt is based not on ion selectivity but on ion concentrations and competitive binding because of a much higher Na+ concentration under physiological conditions.
Abstract: The Na+-coupled melibiose symporter MelB, which can also be coupled to H+ or Li+ transport, is a prototype for the glycoside-pentoside-hexuronide:cation symporter family. Although the 3-D x-ray crystal structure of Salmonella typhimurium MelB (MelBSt) has been determined, the symport mechanisms for the obligatory coupled transport are not well understood. Here, we apply isothermal titration calorimetry to determine the energetics of Na+ and melibiose binding to MelBSt, as well as protonation of this transporter. Studies of the thermodynamic cycle for the formation of the Na+-MelBSt-melibiose ternary complex at pH 7.45 reveal that the binding of Na+ and melibiose is cooperative. The binding affinity for one substrate (Na+ or melibiose) is increased by the presence of the other by about eightfold. The coupling free energies (ΔΔG) of either substrate binding are ∼5 kJ/mol, and binding of both substrates releases a free energy of ∼35 kJ/mol. Measurements of the Na+-binding enthalpy at three different pH values, including the pKa value of MelB, indicate that the binding of one Na+ displaces one H+ per MelBSt molecule. In addition, the absolute dissociation constants for Na+ and H+, determined by competitive binding, show that MelBSt is selective for H+ over Na+ by ∼1,000-fold at a pKa of 6.25. Thus, the Na+ coupling in MelBSt is based not on ion selectivity but on ion concentrations and competitive binding because of a much higher Na+ concentration under physiological conditions. Such a selectivity feature seems to be common for membrane transport proteins that can bind both H+ and Na+ at a common site.

24 citations

Journal ArticleDOI
TL;DR: All four of the saccharide-inhibitable binding activities of Bradyrhizobium japonicum may be mediated by the same mechanism(s) or molecular component(s).
Abstract: Bradyrhizobium japonicum (R110d) exhibited four saccharide-specific binding activities: (a) adsorption to Sepharose beads containing covalently coupled lactose; (b) homotypic agglutination through one pole of the cell (star formation); (c) heterotypic adhesion to the cultured soybean cell line, SB-1; and (d) attachment to roots of soybean plants. Each of these binding activities can be inhibited by the addition of galactose or lactose, but not by derivatives such as N-acetyl-D-galactosamine or melibiose. Treatment of wild-type bacteria with N-methyl-N'-nitro-N-nitrosoguanidine followed by selection on the basis of reduced binding to SB-1 cells, resulted in two specific mutants, designated N4 and N6. Compared to wild type, these two mutants also exhibited decreased binding activity in: (a) adsorption to lactose-Sepharose beads; (b) homotypic star formation; and (c) heterotypic attachment to roots of soybeans plants. These results suggest that all four of the saccharide-inhibitable binding activities of Bradyrhizobium japonicum may be mediated by the same mechanism(s) or molecular component(s).

24 citations


Network Information
Related Topics (5)
Yeast
31.7K papers, 868.9K citations
85% related
Gel electrophoresis
26K papers, 1.1M citations
83% related
Escherichia coli
59K papers, 2M citations
83% related
Operon
14.6K papers, 768.6K citations
82% related
Saccharomyces cerevisiae
32.1K papers, 1.6M citations
82% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20236
202212
202112
202017
201913
201816