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.
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TL;DR: It is concluded from experiments that Tyr-26, Phe-27, P he-29, Leu-321, and His-322 either directly or indirectly mediate sugar recognition in the lactose carrier of E. coli.
Abstract: The purpose of this research was to identify amino acid residues that mediate substrate recognition in the lactose carrier of Escherichia coli. The lactose carrier transports the alpha-galactoside sugar melibiose as well as the beta-galactoside sugar lactose. Mutants from cells containing the lac genes on an F factor were selected by the ability to grow on succinate in the presence of the toxic galactoside beta-thio-o-nitrophenylgalactoside. Mutants that grew on melibiose minimal plates but failed to grow on lactose minimal plates were picked. In sugar transport assays, mutant cells showed the striking result of having low levels of lactose downhill transport but high levels of melibiose downhill transport. Accumulation (uphill) of melibiose was completely defective in all of the mutants. Kinetic analysis of melibiose transport in the mutants showed either no change or a greater than normal apparent affinity for melibiose. PCR was used to amplify the lacY DNA of each mutant, which was then sequenced by the Sanger method. The following six mutations were found in the lacY structural genes of individual mutants: Tyr-26-->Asp, Phe-27-->Tyr, Phe-29-->Leu, Asp-240-->Val, Leu-321-->Gln, and His-322-->Tyr. We conclude from these experiments that Tyr-26, Phe-27, Phe-29 (helix 1), Asp-240 (helix 7), Leu-321, and His-322 (helix 10) either directly or indirectly mediate sugar recognition in the lactose carrier of E. coli.
21 citations
01 Jan 2011
TL;DR: From this study, the optimum conditions that favours the growth of all the group of organisms was found to be pH 6, 30 0 C, 0.2% of the salts used and a significant population of both Yeasts and Molds utilized glucose as their best carbon source.
Abstract: Based on the previous knowledge of spontaneously fermenting maize for the preparation of Ogi, four growth media were used for the isolation of the different common group of organisms implicated. Yeasts and Molds were identified as Saccharomyces cerevisiae, Candida sp., Rhodotorula sp., Aspergillus niger and Penicillium sp. The bacteria were Lactobacillus plantarum, Lactobacillus brevis, Lactobacillus fermentum, Streptococcus lactis, Enterococcus feacalis, Escherichia coli, Staphylococcus aureus, Enterobacter sp., Citrobacter sp., Klebseilla sp., Bacillus subtilis, Bacillus cereus, Bacillus licheniformis, Aerobacter sp., and Corynebacteria sp. A sharp decrease in pH of fermenting gruel from 5.7 to 3.5 was observed within 24 hours while titratable acidity increases within the first 48 hours with a further increase and decrease in pH and titratable acidity at 72 hours.These isolates were subjected to pH ranges of 3.5 – 6 and all were able to grow at optimum pH 6 with a reduction in the number of isolates as pH reduces. Growth in temperature ranging from 25 0 C to 50 0 C, salt (NaCl, MgS0 4, K 2HP0 4, CuS0 4 and ZnS0 4) and sugar (glucose, sucrose, lactose, melibiose and raffinose) concentrations of 0.2% to 1% were carried out on all the isolates. With increase in temperature and salt concentration, a reduction in the number of isolates that grew was observed. From this study, the optimum conditions that favours the growth of all the group of organisms was found to be pH 6, 30 0 C, 0.2% of the salts used and a significant population of all the group of organisms utilized glucose as their best carbon source.
21 citations
TL;DR: In this article, the authors separated reducing carbohydrates in maple syrup and maple sugar by capillary electrophoresis using derivatization with 1-phenyl-3-methyl-5-pyrazolone (PMP) and the characteristics of these samples were studied.
Abstract: Reducing carbohydrates in maple syrup and maple sugar were separated by capillary electrophoresis using derivatization with 1-phenyl-3-methyl-5-pyrazolone (PMP) and the characteristics of these samples were studied. Reducing carbohydrate standards including nine monosaccharides and five disaccharides as PMP derivatives could be easily resolved by using 200 mM borate buffer (pH 10.5) as a background electrolyte. Glucose was the most abundant reducing sugar in both maple samples, and mannose was abundant relative to the other sugars. The other monosaccharides (xylose, arabinose, ribose, galactose and N-acetylglucosamine) were also detected. When maple syrup and maple sugar were treated with invertase, which removed fructose residues from the reducing ends of fructosyl saccharides, melibiose was detected, suggesting that raffinose exists in both samples. The differences of carbohydrate contents between maple syrup and maple sugar were also discussed.
21 citations
TL;DR: The results indicate that maltose shares a common transport system with sucrose and that there may be some interaction between the uptake systems for lactose, cellobiose, and glucose.
Abstract: Trichosporon cutaneum is shown to utilize six disaccharides, cellobiose, maltose, lactose, sucrose, melibiose, and trehalose. T. cutaneum can thus be counted with the rather restricted group of yeasts (11 to 12% of all investigated) which can utilize lactose and melibiose. The half-saturation constants for uptake were 10 +/- 3 mM sucrose or lactose and 5 +/- 1 mM maltose, which is of the same order of magnitude as those reported for Saccharomyces cerevisiae. Our results indicate that maltose shares a common transport system with sucrose and that there may be some interaction between the uptake systems for lactose, cellobiose, and glucose. Lactose, cellobiose, and melibiose are hydrolyzed by cell wall-bound glycosidase(s), suggesting hydrolysis before or in connection with uptake. In contrast, maltose, sucrose, and trehalose seem to be taken up as such. The uptake of sucrose and lactose is dependent on a proton gradient across the cell membrane. In contrast, there were no indications of the involvement of gradients of H+, K+, or Na+ in the uptake of maltose. The uptake of lactose is to a large extent inducible, as is the corresponding glycosidase. Also the glycosidases for cellobiose, trehalose, and melibiose are inducible. In contrast, the uptake of sucrose and maltose and the corresponding glycosidases is constitutive.
21 citations
TL;DR: Cell-free extracts have been prepared from virtually pure cultures of Epidinium ecaudatum Crawley, a protozoon which may be abundant in the rumen of cows feeding on red clover, and the amylase has been shown to be an α-amylase with optimum activity in the pH range 5.3–6.5 and in the temperature range 37°–45°c.
Abstract: Summary Cell-free extracts have been prepared from virtually pure cultures of Epidinium ecaudatum Crawley, a protozoon which may be abundant in the rumen of cows feeding on red clover. Water extracts contain an amylase while phosphate buffer extracts contain the same amylase together with a less soluble maltase and occasionally a cellobiase. Invertase and β-glucosidase were absent from the extracts which were also unable to hydrolyse lactose, melibiose, α-trehalose and cellulose. The amylase has been shown to be an α-amylase with optimum activity in the pH range 5.3–6.5 and in the temperature range 37°–45°c. The final products of the action of the amylase on starch are maltose (major component) and glucose and maltotriose (minor components). Intact clover-starch granules were apparently hydrolysed by the amylase but potato-starch granules were not attacked.
21 citations