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.

Changes in the concentration of carbohydrates during the soaking of soybeans for tempe production

Abstract: Summary Soybeans were soaked for 24h in tap water at 30°C in preparation for tempe fermentation. Soaking was conducted under conditions that give a microbial fermentation, and in the presence of antibiotics where microbial growth was inhibited. Sucrose, stachyose and raffinose were the main di- and oligosaccharides in the beans, and their concentrations decreased by 84, 65 and 50%, respectively, during soaking. Glucose, fructose and galactose were found in the soak-water along with lesser amounts of sucrose, melibiose, raffinose and stachyose. Glucose was the main substrate for microbial growth in the soak-water. The concentrations of mono-, di-and oligosaccharides in the beans and in the soak-water were determined by the activity of invertases and α-galactosidases endogenous to the beans, diffusion of the sugars into and out of the bean, and the species of micro-organism growing in the soak-water.

The toxin-binding protein of sugarcane, its role in the plant and in disease development.

Abstract: The toxin-binding protein of sugarcane susceptible to eyespot disease also possesses raffinose-binding activity. The Km's for binding are: helminthosporoside (toxin) 6.8 × 10-5 M, raffinose 2.5 × 10-5 M, and melibiose 2.6 × 10-5 M. Evidence obtained by administering [14C]raffinose to sugarcane protoplasts suggests that this protein participates in α-galactoside transport. Cells from a resistant clone of sugarcane do not possess an active-binding protein, and likewise, do not actively take up raffinose. Interestingly, the K+, Mg++ ATPase (ATP phosphohydrolase, EC 3.6.1.3.) on the plasma membrane of the susceptible sugarcane is 30% activated by the toxin at 3 mM. In addition, toxin-treated tissue slices show a rapid uptake of 86Rb+-K+ which is in agreement with the toxin activation of the membrane K+, Mg++ ATPase. Since the ATPase does not directly interact with the toxin, the activation effect occurs by means of the toxin-binding protein. Membrane proteins may be influenced by the toxin-binding protein acting by one of several different mechanisms.

Positive selection for resistance to 2-deoxyglucose gives rise, in Streptococcus salivarius, to seven classes of pleiotropic mutants, including ptsH and ptsI missense mutants.

Abstract: Summary We have used the toxic non-metabolizabie glucose/ mannose analogue 2-deoxygiucose to isolate a comprehensive collection of mutants of the phosphoenoipyruvate:sugar phosphotransferase system from Streptococcus salivarius. To increase the range of possible mutations, we isolated spontaneous mutants on different media containing 2-deoxyglucose and various metabolizable sugars, either lactose, meli-biose, galactose or fructose. We found that the frequency at which 2-deoxygiucose-resistant mutants Were isolated varied according to the growth substrate. The highest frequency was obtained with the combination galactose and 2-deoxygiucose and was 15-fold higher than the rate observed with the mixture melibiose and 2-deoxygiucose, the combination that gave the lowest frequency. By combining results from: (i) Western biol analysis of IIIMan, a specific component of the phosphoenolpyruvate:mannose phosphotransferase system in S. salivarius; (ii) rocket immunoelectrophoresis of HPr and EI, the two general energy-coupling proteins of the phosphotransferase system; and (iii) from gene sequencing, mutants could be assigned to seven classes. Class 1 was composed of strains devoid of IIIManL, a low-molecular-weight form of IIIManL (35200), class 2 was composed of strains exhibiting a reduced level of IIIManL, class 3 was composed of strains devoid of both forms of IIIMan (IIIManL as well as IIIManH, the high-molecular-weight form of IIIMan (38900)), class 4 was composed of mutants bearing a mutation in ptsH, the gene encoding HPr, class 5 was composed of mutants bearing a mutation in ptsl, the gene encoding EI, class 6 was composed of 2-deoxygiucose-resistant strains without any apparent defect in PTS components, and class 7 was composed of strains possessing both forms of IIIMan but abnormal levels of HPr and/or EI without any mutation in the ptsH and/or the ptsI genes. Preliminary characterization of representative strains of each class is reported.

Expression of Rice (Oryza sativa L. var. Nipponbare) α-Galactosidase Genes in Escherichia coli and Characterization

Abstract: Two putative α-galactosidase genes from rice (Oryza sativa L. var. Nipponbare) belonging to glycoside hydrolase family 27 were cloned and expressed in Escherichia coli. These enzymes showed α-galactosidase activity and were purified by Ni Sepharose column chromatography. Two purified recombinant α-galactosidases (α-galactosidase II and III; α-Gal II and III) showed a single protein band on SDS–PAGE with molecular mass of 42 kDa. These two enzymes cleaved not only α-D-galactosyl residues from the non-reducing end of substrates such as melibiose, raffinose, and stachyose, but also liberated the galactosyl residues attached to the O-6 position of the mannosyl residue at the reducing-ends of mannobiose and mannotriose. In addition, these enzymes clipped the galactosyl residues attached to the inner-mannosyl residues of mannopentaose. Thus, α-Gal II catalyzes efficient degalactosylation of galactomannans, such as guar gum and locust bean gum.