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.

An NAD + , Mn 2+ and DTT-dependent α-galactosidase from Bacillus halodurans

Abstract: The α-galactosidase mel4A (previously called melA) gene of Bacillus halodurans was recombinantly expressed in Escherichia coli, purified and characterized. The mel4A gene consists of 1305 nucleotides encoding a protein of 434 amino acids with a predicted molecular weight of 49,761. According to its primary structure as deduced from the nucleotide sequence of the gene, Mel4A was assigned to family 4 of glycoside hydrolases. Almost all of the enzyme was produced as inclusion bodies at 37C in E. coli. In order to reduce the expression level, cultivation temperature was decreased to 20C so that the enzyme could be collected from soluble fraction. Recombinant α-galactosidase Mel4A was purified to homogeneity in a single step using His-binding metal affinity chromatography. B. halodurans Mel4A has the unusual property, i.e., absolutely depending on NAD and Mn for activity. Co and Ni also activated Mel4A, albeit less efficiently than Mn. In addition, Mel4A activity required reducing condition which met by the addition of dithiothreitol (DTT). In the presence of all cofactors, optimum activity was achieved at 37C and pH 7.4. The enzyme hydrolyzed p-nitrophenyl-α-D-galactopyranoside, melibiose, raffinose, and stachyose but not guar gum, indicating that this enzyme preferred small saccharides to highly polymerized galactomannans. Western immunoblots of intracellular and extracellularproteins of B. halodurans revealed that raffinose induced the expression of intracellular Mel4A of B. halodurans. This bacterium was also able to utilize guar gum as the carbon source, but Western blot analysis indicated that the production of Mel4A was not enhanced by the addition of guar gum.

Vaccine, antibody and antibody-containing composition for treating infectious disease with streptococcus sanguis

Abstract: PURPOSE:A vaccine for an infectious disease with Streptococcus sanguis, containing an antigen derived from a mold of a bacterium belonging to the genus Streptococcus having high pathogenic properties and decomposition ability of raffinose and melibiose, as an active ingredient. CONSTITUTION:A mammal is immunized against an antigen derived from a group of part or more of a mold of a bacterium [e.g., Streptococcus sanguis SSH83 (FERM P-7372), Streptococcus sanguis MCLS (FERM P-8169)] having high pathogenic properties and decomposition ability of raffinose and melibiose, to produce an antibody in the animal body, an antibody for treating a human disease (e.g., Kawasaki's disease) induced or deteriorated with the bacterium and blended with a carrier or an excipient, to given the aimed vaccine.

Immunochemical specificities of the combining sites of bovine immunoglobulins reactive with sepharose 4B.

Abstract: Binding specificities of calcium-dependent and -independent bovine IgM and IgG reactive with unsubstituted Sepharose 4B were determined by competitive binding assays. The binding of 125I-labeled calcium-dependent bovine IgM to unsubstituted Sepharose 4B was most effectively inhibited by lactose which was about 100 times more reactive than galactose and melibiose. Other inhibitors were much less potent. With 125I-labeled calcium-independent bovine IgM and IgG, on the other hand, lactose was as potent as galactose. Melibiose was about 10 times less potent than lactose and galactose, whereas other mono- and disaccharides were much less potent. From these findings, the combining site of calcium-dependent bovine IgM reactive with unsubstituted Sepharose 4B may be specific for lactose, whereas those of calcium-independent bovine IgM and IgG specific for galactose.

Melibiose operon expression system

Abstract: The present invention relates to new vectors expressible in a host comprising the promoter region of the melibiose operon operably linked to a transcriptional unit comprising a nucleic acid sequence which is heterologous to said host, whereas the expression of said nucleic acid sequence is controlled by said promoter region of the melibiose operon Also disclosed are, the use of said new vector for the regulated heterologous expression of a nucleic acid sequence in a prokaryotic host, an isolated and purified nucleic acid sequence expressible in a host comprising the promoter region of the melibiose operon operably linked to a transcriptional unit comprising a nucleic acid sequence which is heterologous to said host, whereas the expression of said nucleic acid sequence is controlled by said promoter region of the melibiose operon, a prokaryotic host transformed with said vector or said isolated and purified nucleic acid sequence, and a method for producing a polypeptide in a host using said vector

Cellular heterogeneity and MTH1 play key roles in galactose mediated signaling of the GAL switch to utilize the disaccharide melibiose

Abstract: Yeast metabolizes the disaccharide melibiose by hydrolyzing it into equimolar concentrations of glucose and galactose by MEL1-encoded -galactosidase. Galactose metabolizing genes (including MEL1) are induced by galactose and repressed by glucose, which are the products of melibiose hydrolysis. Therefore, how melibiose catabolization and utilization take place by circumventing the glucose repression is an enigma. Other than the galactose metabolizing genes MTH1, a negative regulator of glucose signal pathway has Gal4p binding sites and is induced by galactose and repressed by high glucose concentration. But, at low or no glucose MTH1 along with its paralogue STD1 represses hexose transporters, that are involved in glucose transport. This sort of tuning of glucose and galactose regulation motivated us to delineate the role of MTH1 as a regulator of MEL1 expression and melibiose utilization. The deletion mutant of MTH1 shows growth defect on melibiose and this growth defect is enhanced upon the deletion of both MTH1 and its paralogue STD1. Microscopy and flowcytometry analysis, suggest, that even though MEL1 and GAL1 promoter are under Gal4p and Gal80p regulation, upon deletion of MTH1 it hampers only MEL1 expression, but not the GAL1 gene expression. By using 2-Deoxy galactose toxicity assay, we observed phenotypic heterogeneity in cells grown on melibiose i.e. after cleaving of melibiose a fraction of cell population utilizes glucose and another fraction utilizes galactose and coexist together. Understanding GAL/MEL gene expression patterns in melibiose will have great implication to understand various other complex sugar utilizations, tunable gene expressions and complex feedback gene regulations. SignificanceSugar metabolism is an important phenomenon to understand the regulation of gene expression. Glucose is the most preferred carbon source. Yeast follows glycolytic pathways like cancer cells for metabolism of sugars and understanding this will throw more light to the metabolism of cancer cells. In this communication we observed cell-to-cell heterogeneity in yeast cells playing a key role in metabolism of a complex disaccharide melibiose, which gets cleaved into glucose and galactose by -galactosidase. Glucose represses -galactosidase and galactose induces it. Because of the heterogeneous population of cells one fraction consumes glucose liberated by melibiose hydrolysis, therefore it is not sufficient to repress -galactosidase and other GAL genes. Therefore, GAL genes are expressed and help in metabolizing melibiose and galactose.