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At least 937 records · Page 52Linked to original sources
PubMed1979

Activity of pectinases, amylases, and saccharase in Pythium spp.

The activity of pectine-lyase, polygalacturonase, pectine-methyl-esterase, amylase, and saccharase in Pythium ultimum, Pythium oligandrum, and Pythium debaryanum was determined. Cultures of fungi were cultivated under different temperatures and pH-values within 24 hours and 15 days. The optimum temperature for production of the mentioned enzymes was found to be 24 degrees C. Furthermore, the influence of pH and age of culture on activity of enzyme was investigated. The same trend was found in all the fungus species examined.

Amylases↗
PubMed2005

Triterpene glycosides of Siraitia grosvenori inhibit rat intestinal maltase and suppress the rise in blood glucose level after a single oral administration of maltose in rats.

The effect of the crude extract from Siraitia grosvenori Swingle (SG-ex) on the postprandial rise in blood glucose level was investigated. The increase in plasma glucose level in response to the oral administration of maltose was significantly suppressed in rats when SG-ex was given orally 3 min before the maltose administration. There was, however, no effect when glucose was administered instead, suggesting that the antihyperglycemic effect of SG-ex is elicited by inhibition of maltase in the small intestinal epithelium. In vitro, SG-ex inhibited rat small intestinal maltase. Similar effects were also observed both in vivo and in vitro when the concentrate of the sweet elements (triterpene glycosides) prepared from SG-ex was used. Furthermore, the main sweet element of SG-ex, mogroside V, and some minor elements such as mogroside IV, siamenoside I, and mogroside III also exhibited maltase inhibitory effect with IC50 values of 14, 12, 10, and 1.6 mM, respectively. These results suggest that SG-ex exerts anti-hyperglycemic effects in rats by inhibiting maltase activity and that these effects are at least partially exerted by its sweet elements, triterpene glycosides.

Animals↗
PubMed2005

Phenolic and triterpene glycosides from the stems of Ilex litseaefolia.

Chemical investigation on the stems of Ilex litseaefolia afforded four new phenolic glycosides, litseaefolosides A-D (1-4), and two new triterpene glycosides, spathodic acid 28-O-beta-d-glucopyranoside (5) and (20S)-niga-ichigoside F1 (6), along with 28 known compounds. The structures of 1-6 were determined on the basis of chemical and spectroscopic evidence. Litseaefoloside C (3) showed inhibitory activities in vitro for alpha-glucosidase and lipase with IC(50) values of 34.0 and 0.31 microg/mL, respectively.

Enzyme Inhibitors↗
PubMed1995

Mechanism-based inhibition of yeast alpha-glucosidase and human pancreatic alpha-amylase by a new class of inhibitors. 2-Deoxy-2,2-difluoro-alpha-glycosides.

2-Deoxy-2,2-difluoroglycosides are a new class of mechanism-based inhibitors of alpha-glycosidases, which function via the accumulation of a stable difluoroglycosyl-enzyme intermediate. Two members of this new class of inhibitor have been synthesized and kinetic studies performed with their target glycosidases. Thus 2,4,6-trinitrophenyl 2-deoxy-2,2-difluoro-alpha-glucoside is shown to inactivate yeast alpha-glucosidase with a second order rate constant of ki/Ki = 0.25 min-1 mM-1. The equivalent difluoromaltoside inactivates human pancreatic alpha-amylase with ki/Ki = 0.0073 min-1 mM-1. Competitive inhibitors protect the enzyme against inactivation in each case, showing reaction to occur at the active site. A burst of release of one equivalent of trinitrophenolate observed upon inactivation of human pancreatic alpha-amylase proves the required 1:1 stoichiometry. These are the first mechanism-based inhibitors of this class to be described, and the first mechanism-based inhibitors of any sort for the medically important alpha-amylase. In addition to having potential as therapeutics, compounds of this class should prove useful in subsequent structural and mechanistic studies of these enzymes.

Carbohydrate Sequence↗
PubMed1978

P-Nitrophenol-alpha-D-glucopyranoside as substrate for measurement of maltase activity in human semen.

Hitherto, seminal plasma maltase has been measured with maltose as substrate; this method is time consuming and lacks specificity. The use of a synthetic substrate, p-nitrophenol-alpha-D-glucopyranoside, allows accurate and rapid determination of this activity. When maltase is added to the incubation medium (the substrate and reduced glutathione in potassium phosphate buffer, pH 6.8), maintained at 37 degrees C, hydrolysis of the original substrate to p-nitrophenol goes at a constant rate during 4 h. Under optimal conditions of incubation, the Michaelis constant of the reaction, calculated by the Hanes method, was 2.92 +/- 0.84 (SD) X 10(-3) for six different semen samples. Isomaltase appeared to be absent from seminal plasma. The enzyme is stable to freezing and slow thawing and can be stored for at least 26 days at -80 degrees C. Its molecular weight is 259 000. Tris(hydroxymethyl)aminomethane (pH 6.8) exerts a noncompetitive inhibition on the enzyme activity. In 68 men 23 to 45 years old, whose semen analyses were normal, the seminal plasma maltase activity was 467 +/- 135 (SD) mU/g of protein. It was generally decreased in patients with infertility disorders.

Adult↗
PubMed1989

Castanospermine-glucosides are potent, selective, long-acting sucrase inhibitors.

Castanospermine-glucosides (CS-glcs) are new compounds which have been evaluated as glycohydrolase inhibitors in rats. 7-O-alpha-D-Glucopyranosyl-CS (7 alpha-glc-CS) and 8 alpha-glc-CS were potent sucrase inhibitors with IC50s of 40 and 30 nM, respectively. Their sucrase inhibition was poorly reversible. They were much weaker liver lysosomal alpha-glucosidase inhibitors with IC50s of 40,000 nM. 1 alpha-glc-CS and 8 beta-glc-CS were both weaker and less selective sucrase inhibitors. In vivo, 7 alpha-glc-CS and 8 alpha-glc-CS effectively reduced the glycemic response to an oral 2 g/kg sucrose load at doses less than or equal to 1 mg/kg. 8 alpha-glc-CS was effective when administered up to 4 hr before sucrose. The known glucohydrolase inhibitors 1-deoxynojirimycin and N-hydroxyethyl-1-deoxy-nojirimycin were also potent sucrase inhibitors (IC50s = 200 and 400 nM, respectively) but their sucrase inhibition was readily reversible in vitro and their in vivo duration of action was much shorter than for the CS-glcs. Among the glucohydrolase inhibitors tested, the prolonged in vivo duration of action could be predicted by poor reversibility from sucrase. These CS-glcs provide a new generation of sucrase inhibitors which may be useful in the treatment of diabetes mellitus.

Alkaloids↗
PubMed1983

Preliminary study of the pectolytic activity of Cryptococcus albidus var. albidus.

A preliminary study was done on the pectolytic activity of Cryptococcus albidus var. albidus. Cell-free culture broths of six strains of this yeast species were shown to degrade pectin hydrolytically by means of a polygalacturonase-pectinmethylesterase system. Neither pectin nor pectate lyase activities were detected.

Carboxylic Ester Hydrolases↗