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.

Enzymatic regioselective deprotection of peracetylated mono- and disaccharides

Abstract: Selective enzymatic hydrolysis of the peracetylated disaccharides, namely cellobiose, lactose, maltose and melibiose, with lipase from Asperilligus niger in aqueous buffer and organic solvent for 30 min afforded exclusively the corresponding heptaacetates with a free hydroxyl group at C-1 in high yield. Prolonged reaction of the β-1,4 linked cellobiose and lactose peracetates afforded selectively their hexaacetates with free hydroxyl groups at C-1,2, whereas the α-1,4 linked disaccharides maltose and melibiose peracetate gave a complex mixture of products. The reaction of 2-acetamido-2-deoxy-1,3,4,6-tetra-O-acetylglucopyranose (11) for 22 h afforded as the major product the diacetate 12 with free hydroxyl groups at C-1,4.

[102] Trehalase from insects

Abstract: Publisher Summary This chapter discusses the synthesis of trehalase from insects. The activity of the enzyme is determined by measurement of the production of reducing sugar using the Nelson–Somogyi method. The enzyme is specific for trehalose, with no activity toward the following substrates: maltose, sucrose, melibiose, lactose, raffinose, and turanose. The reagents used, procedure followed, and the steps involved in the purification are also described in the chapter. One unit of activity is equivalent to 1 micromole of glucose produced per minute at 32°. The activity of the enzyme is maximal at pH 5.6 and half maximal at pH 4.0 and 8.0. The enzyme is maximally active at 45° and rapidly becomes inactivated above this temperature, so that under standard assay conditions activity is decreased by 50% at 55°. Dahlqvist has isolated trehalase from hog small intestine, using PO4 buffer pH 6.0 for elution from a diethylaminoethyl (DEAE)-cellulose column, pH optimum about 6.0; Ks = 3 × 10 –3 M α,α-trehalose.

A Halophilic Vibrio Isolated from a Case of Chronic Cholecystitis

Abstract: We found a halophilic vibrio in B bile from a 75-year-old female patient with chronic cholecystitis, and examined its biochemical characteristics. The organisms are gram-negative short rods or comma shaped, with some ring forms. They have a single polar flagellum, but not capsule. The strains can grow in peptone water with 1.0 to 4.0% NaC1, but not with no NaC1 or 6.0% NaC1. The characteristics of the organisms are positive dextrose fermentation, catalase, oxidase, and ornithine decarboxylase, and negative lysine decarboxylase, arginine dihydrolase, and absence of gas from glucose. They are sensitive to 2,4-diamine-6,7-diisopropyl pteridine (0/129). These characteristics indicate that the isolated strain should be a halophilic vibrio. however, no growth on Salmonella-Shigella (SS), SS with added sucrose and bromcresol purple (SS-SB), MacConkey's or thiosulfate citrate bile salts (TCBS) agar plates was demonstrated. Nitrate reduction, Simmons' citrate agar, indole, omicron-nitrophenol-beta-d-galactopyranoside (ONPG), motility and esculin hydrolysis were positive. Urease, gelatinase, Voges-Proskauer, phenylalanine deaminase and malonate reactions were negative. Acid was produced from amygdalin, arabinose, cellobiose, fructose, galactose, glucose, lactose, maltose, mannitol, salicin, starch, sucrose, trehalose, and xylose, but not from adonitol, dulcitol, inositol, mannose, melibiose, raffinose, rhamnose and sorbitol. From these characteristics the isolate is considered to be not identical with V. parahaemolyticus, V. Cholerae, V. Vulnificus or other vibrios. It can be presumed that this isolate represents another species of halophilic vibrio.

Blood Group Substance-degrading Enzymes Obtained from Streptomyces sp.: Part II. Purification and Characteristics of α-Galactosidase from Streptomyces 9917S2

Abstract: The blood group B substance-degrading activity of Streptomyces 9917S2 is induced by galactosides as α-galactosidase activity is. Purification of the α-galactosidase was attempted by chromatography on DEAE-Sephadex and Sephadex. The purified preparation was shown to be free from α- and β-glucosidases, β-galactosidase, α- and β-glucosaminidases, and α- and β-galactosaminidases activities. The blood group B substance-degrading activity was present only in this fraction. This enzyme preparation cleaves α-(1→3)- and α-(1→6)-galactosidic linkages. The activity is inhibited by d-galactose, melibiose, and raffinose and also by l-arabinose and d-xylose.

[Purification and characterization of alpha-glucosidase from an extreme thermophile, Thermus thermophilus HB 8].

Abstract: A highly thermostable alpha-glucosidase (E C.3.2.1.20) from an extreme thermophile, Thermus thermophilus HB 8, was purified to homogeneous by ammonium sulfate fractionation, DEAE-cellulose chromatography and preparative slab gel electrophoresis. The enzyme was purified 17 fold with 21% recovery of activity. The enzyme had a molecular weight of 67000 by SDS-PAGE. The isoelectric point was pH4.5 by IEF on PAG. The enzyme hydrolized p-nitrophenyl-alpha-glucoside (PN-PG), sucrose and maltose, but not cellobiose, melibiose and soluble starch. The km value for PNPG was 0.4mmol/L, the Vmax was 0.29 mumol.min-1.mg-1. The enzyme exhibited high thermostability. After incubation at 90 degrees C for 10 h in 50 mmol/L acetate buffer pH 5.8, the enzyme retained 90% of its original activity. The half-live (t1/2) at 95 degrees C was 108 min. The enzyme was activated by Mg2+, Mn2+, Ca2+, Ba2+ and strongly inhibited by Hg2+, Cu2+. Modification of the enzyme by EDC or DEPC led to complete loss of activity, which suggests that carboxyl group(s) and histidine residue(s) are essential for activity of alpha-glucosidase.