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.

Phenotypic characterization of Microsporum canis isolated from cats and dogs.

Abstract: To characterize strains of Microsporum canis that infect dogs and cats in Sao Paulo city, 30 isolates of this dermatophyte were tested for their ability to assimilate carbon and nitrogen sources, for proteinase and phospholipase secretion, for susceptibility to yeast killer toxins, and for susceptibility to the antifungals fluconazole, ketoconazole, itraconazole, 5-fluorocytosine and amphotericin B, in E test. All samples assimilated the nitrogen sources asparagine, ammonium sulphate, urea and sodium nitrate, as well as the carbon sources inulin, mannitol, trehalose, meso-erythritol, maltose, mannose, sorbitol, cellobiose, fructose and dextrin. Not all the samples assimilated adonitol, galactose, arabinose, rhamnose, raffinose, melibiose, ribose and sucrose, and none of them was capable of growing with dulcitol, lactose, or xylose as the only carbon source. Proteinase and phospholipase secretion was observed for most isolates. In the test of yeast killer toxin, 10 types could be identified, with four types exclusively observed in isolates from dogs and two types exclusively observed in isolates from cats. In the E test, all isolates were found to be resistant to the fluconazole and 5-fluorocytosine, while they were variably sensitive to amphotericin B, ketoconazole and itraconazole. When the data were submitted to the qualitative analysis in the matrix distance program FITOPAC, the similarity of the isolates could be assessed.

Efficient and regioselective synthesis of globotriose by a novel α-galactosidase from Bacteroides fragilis.

Abstract: Globotriose (Galα1–4Galβ1–4Glc) is an important cell surface epitope that acts as the receptor for Shiga-like toxins, and it is also the core structure of Globo H and SSEA4 that are tumor-associated glycans. Hence, the enzymatic synthesis of globotriose would be necessary for the development of carbohydrate-based therapeutics for bacterial infections and cancers. Here, a novel GH27 α-galactosidase gene (agaBf3S), a 1521-bp DNA encoding 506 amino acids with a calculated molecular mass of 57.7 kDa, from Bacteroides fragilis NCTC9343 was cloned and heterogeneously expressed in Escherichia coli. The recombinant enzyme AgaBf3S preferentially hydrolyzed p-nitrophenyl-α-D-galactopyranoside (pNPαGal) in all tested nitrophenyl glycosides. It showed maximum activity at pH 4.5 and 40 °C, and it was stable at pH 4.0–11.0 below 40 °C and metal-independent. The K m and k cat values for pNPαGal, melibiose, and globotriose were 1.27 mM and 172.97 S−1, 62.76 mM and 17.74 S−1, and 4.62 mM and 388.45 S−1, respectively. AgaBf3S could transfer galactosyl residue from pNPαGal to lactose (Galβ1–4Glc) with high efficiency and strict α1–4 regioselectivity. The effects of initial substrate concentration, pH, temperature, and reaction time on transglycosylation reaction catalyzed by AgaBf3S were studied in detail. AgaBf3S could synthesize globotriose as a single transglycosylation product with a maximum yield of 32.4 % from 20 mM pNPαGal and 500 mM lactose (pH 4.5) at 40 °C for 30 min. This new one-enzyme one-step synthetic reaction is simple, fast, and low cost, which provides a promising alternative to the current synthetic methods for access to pharmaceutically important Galα1–4-linked oligosaccharides.

The lactose system in Klebsiella aerogenes V9A 2. Galactoside permeases which accumulate lactose or melibiose

Abstract: Klebsiella aerogenes V9A possesses at least three galactoside permeases, the lactose permease (LacP), the melibiose permease (MelP) and a third permease (GPIII), and also a galactose permease. It is shown that the first three of these permeases all accumulate both lactose and melibiose efficiently, while the galactose permease takes up neither sugar. Lactose only induces LacP and melibiose only induces MelP. d -fucose, isopropyl-β- d -thiogalactoside (IPTG) and methyl-β- d -thiogalactoside (TMG) all induce GPIII, but galactose does not. GPIII takes up both lactose and melibiose but cannot accumulate lactose in the presence of IPTG. Thus substantial differences are found between the galactoside permeases of Klebsiella and Escherichia coli .

A critical study of the taxonomic value of some tests of assimilation used for the classification of the sporogenous yeasts

Abstract: Six texts of assimilation used in the taxonomy of yeasts, (lactose, maltose, cellobiose, trehalose, melibiose, sucrose) have been critically tested by the examination of intracellular enzymic systems. The results obtained among the sporogenous species ofSaccharomyces, Kluyveromyces, Pichia, Hansenula, Debaryomyces indicate that cellobiose, lactose, maltose and trehalose tests no longer supply an important value for the speciation, because the number of cryptical osidases is so high.

Synthesis of nucleotide-activated disaccharides with β-galactosidase from Bacillus circulans and α-galactosidase from Bifidobacterium adolescentis

Abstract: The enzymatic synthesis of nucleotide-activated disaccharides by glycosidase-catalyzed transglycosylation reactions was investigated. High product yields were obtained when the kinetically driven syntheses were performed in frozen aqueous solutions at −5 °C. β-Galactosidase from Bacillus circulans catalyzed the transfer of d -galactose from lactose onto the nucleotide sugar UDP-Gal stereo- and regioselectively, forming the nucleotide disaccharide Gal(β1–4)Gal(α1-UDP. α-Galactosidase from Bifidobacterium adolescentis accepted UDP-Gal and UDP-Glc only when the reaction was performed at −5 °C with melibiose as glycoside donor. Enzyme and donor concentrations were optimized for the preparative synthesis yielding Gal(α1–3)Glc(α1-UDP and Gal(α1–3)Gal(α1-UDP as analyzed by MALDI-TOF mass spectrometry and 1D and 2D 1 H and 13 C NMR spectroscopy. The reported products are invaluable tools for studies on their possible biochemical function as donor substrates or inhibitors of Leloir glycosyltransferases.