Α-glucosidic Linkages Research Articles

Assignment of a p-nitrophenyl α- d-glucopyranosidase of bacillus stearothermophilus ATCC 12016 to a novel exo-α-1,4-glucosidase active for oligomaltosaccharides and α-glucans

A p-nitrophenyl α- d-glucopyranoside-hydrolyzing α-glucosidase of an obligate thermophile, Bacillus stearothermophilus ATCC 12016, was purified to an electrophoretically and immunologically homogeneous state. The specific activity was 113 μmol p-nitrophenyl α- d-glucopyranoside hydrolyzed/min per mg protein at 60°C and pH 6.8. The molecular weight, Stokes radius, sedimentation coefficient (s 20,w), extinction coefficient at 280 nm and pH 6.8, and isoelectric point were estimated as 47 000, 3.06 nm, 3.98 S, 2.88 cm 2 · mg −1 and 5.2, respectively. The NH 2-terminal amino acid of the enzyme was menthionine. Neither carbohydrate nor cysteine residue was present in the enzyme. The pH and temperature optima for activity were 6.3 and 70°C, respectively. The K m for the nitrophenyl glucoside was 0.63 mM. The enzyme produced α-glucose by the cleavage of single glucose units from the non-reducing terminal α-1,4-bonds of maltosaccharides (chain length = 2–6 glucose units), α-limit dextrins, phenyl α- d-maltoside, dextrin, amylose, amylopectin and soluble starch. The α-1,6-bonds in these saccharides, were not attacked. Sucrose, turanose and melezitose were weakly hydrolyzed, while there was no activity towards the α-glucosidic linkages in methyl α- d-glucoside, nigerose, kojibiose, panose, β-limit dextrins, isomaltosaccharides (2–6 glucose units), α- and β-cyclodextrins, pullulan and dextran. The greatly restricted substrate specificity proposed the assignment of the enzyme to an exo-α-1,4-glucosidase. Other catalytic properties, along with amino acid composition, are described in this report.

Sucrase and maltase activities in supragingival dental plaque in humans of streptococcal, actinomyces and lactobacilli species

20 reference strains and 72 isolated strains from dental plaque of streptococci, actinomyces, and lactobacilli species were examined for sucrase and maltase activities. The type of sucrase in the different strains was determined by use of the alpha-glucosidase inhibitor, acarbose. The enzyme activities were determined as formation of monosaccharide, and quantitated spectrophotometrically. Although variations occurred in enzyme activities between reference and isolated strains, the same general pattern was noticed. Strains of Streptococcus mutans and S. salivarius showed regularly the highest sucrase activities, followed by strains of Actinomyces viscosus and A. naeslundii. Most lactobacilli belonged to the bacteria with low sucrase activity like S. sanguis and S. mitior. In some lactobacilli strains, however, a high sucrase activity was observed. The level of sucrase activity in S. mutans strains was dependent on biotype/serotype, as strains of biotype V/serotype e showed high activities, biotypes I and IV corresponding to serotypes c, f, and d showed intermediate activity, and biotype III/serotype a always showed low activity. In most of the strains the sucrases were composed of enzymes with specificity against both alpha-glucosidic linkage and beta-fructosidic linkage of the sucrose molecule, but in varying ratios. In all species, exept S. sanguis and S. mitior, lower maltase than sucrase activity was observed, but even in the two species mentioned the maltase activities were relatively low. On the basis of observations of selected reference strains in every species examined both sucrases and maltases are to some extent inducible.

Tannins of rosaceous medicinal plants. I. Structures of potentillin, agrimonic acids A and B, and agrimoniin, a dimeric ellagitannin.

Four new ellagitannins, potentillin (1), agrimoniin (2), and agrimonic acids A (3) and B (4), have been isolated from the roots of Agrimonia japonica (MIQ.) KOIDZ., and their structures, with an α-glucosidic linkage, were elucidated on the basis of spectral and chemical evidence. Potentillin (1) and agrimoniin (2) have also been isolated from Potentilla kleiniana WIGHT et ARNOTT.

13C-NMR study of the glucose synthesis pathways in the bacterium Chlorobium thiosulfatophilum

Photoassimilation of 13CO 2 and acetate by the photosynthetic bacterium Chlorobium thiosulfatophilum was investigated using 13C-NMR as the method for determination of the labelling pattern of the glucose synthesized by the bacterium. Metabolic pathways functioning in the bacterium were identified by analysis of the multiplet structure of the spectra of tightly coupled systems. The labelling pattern showed that glucose was synthesized in C. thiosulfatophilum mainly by the gluconeogenesis pathway. In agreement with previous investigations, the reserve polysaccharide of C. thiosulfatophilum was shown to be polyglucose, with the glucose units linked predominantly by (1→4)α-glucosidic linkages.

α-Glucosidase activity in haemolymph of the American cockroach, Periplaneta americana

α-Glucosidase activity of whole haemolymph has been investigated in adult males of the American cockroach, Periplaneta americana. Two electrophoretically distinguishable enzymes capable of hydrolysing α-glucosidic linkages are present in the serum component of the haemolymph, and one of these hydrolyses trehalose. Trehalase activity is also present in haemocytes, and the haemocyte enzyme shares an identical electrophoretic mobility and similar pH sensitivity with the serum trehalase. Furthermore, both enzymes are inhibited to the same extent by sodium ethylene diamine tetracetate (EDTA); thus it is suggested that the same enzyme may be responsible for trehalase activity in the two components. The K m of EDTA-inhibited trehalase is 3·3 mM and this value is reduced to 1·8 mM upon activation of the enzyme by calcium ions. The properties of the trehalase are discussed in light of the possible rôle of the enzyme in regulating haemolymph trehalose and glucose concentrations.

Enzymic synthesis of 3-O-alpha-D-glucopyranosyl D-xylose.

TRANSGLYCOSYLATION reactions with microbial enzymes offer a facile method for the synthesis of new oligosaccharides. Following our earlier report1 on the production of 3-O-β-D-glucopyranosyl D-xylose by the action of a cell-free extract of A. niger 152 on a cellobiose–xylose mixture, the corresponding disaccharide containing an α-glucosidic linkage has now been synthesized via the following reaction : catalysed by a transglycosylase from Penicillium lilacinum.