Disaccharidase

Diarrhea is a common problem that is usually self-limiting and of short duration. Increased accumulations of small intestinal and colonic contents are known to be responsible for producing diarrhea. The former may be caused by increased intestinal secretion which may be enterotoxin-induced, eg, cholera and E. col] or hormone and dmg-induced, eg, caffeine, prostaglandins, and laxatives decreased intestinal absorption because of decreased mucosal surface area, mucosal disease, eg, tropical spme, or osmotic deficiency, eg, disaccharidase or lactase deficiency and rapid transit of contents. An increased accumulation of colonic content may be linked to increased colonic secretion owing to hydroxy fatty acid or bile acids, and exudation, eg, inflammatory bowel disease or amebiasis decreased colonic absorption caused by decreased surface area, mucosal disease, and osmotic factors and rapid transit, eg, irritable bowel syndrome. 

N Triadou, J Bataille, J Schmitz. Longitudinal study of the human intestinal brush border membrane proteins. Distribution of the main disaccharidases and peptidases. Gastroenterology 85 1326-1332, 1983. 

Glucose and galactose enter the absorptive cells by way of secondary active transport. Cotransport carrier molecules associated with the disaccharidases in the brush border transport the monosaccharide and a Na+ ion from the lumen of the small intestine into the absorptive cell. This process is referred to as "secondary" because the cotransport carriers operate passively and do not require energy. However, they do require a concentration gradient for the transport of Na+ ions into the cell. This gradient is established by the active transport of Na+ ions out of the absorptive cell at the basolateral surface. Fructose enters the absorptive cells by way of facilitated diffusion. All monosaccharide molecules exit the absorptive cells by way of facilitated diffusion and enter the blood capillaries. 

Disaccharides Disaccharidases Hydrolyze disaccharides into Absorptive cells of Brush border of... 

Aletor, V.A. and B.L. Fetuga. 1988. The interactive effects of lima bean (Phaseolus lunatus) trypsin inhibitor, hemagglutinin and cyanide on some hepatic dehydrogenases, ornithine carbamoyltransferase and intestinal disaccharidases in weanling rats. Veterin. Human Toxicol. 30 540-544. 

Antibiotics, regardless of method of manufacture Certain substances produced by fermentation Disaccharidase inhibitors HMG-CoA inhibitors Synthetic chemicals... 

Digestion of starch involves the hydrolysis of the bonds between the glucose molecules. Two classes of hydrolytic enzymes are required amylases and oligo- and di-saccharidases (Figure 4.5). The disaccharidases are also involved in hydrolysis of sucrose and lactose. 

The late discovery of acetyl xylan and feruloyl esterases has been partly due to the lack of suitable substrates. Xylans are often isolated by alkaline extraction, in which ester groups are saponified. Treatment of plant materials under mildly acidic conditions, as in steaming or aqueous-phase thermomechanical treatment, leaves most of the ester groups intact. These methods, however, partly hydrolyze xylan to shorter fragments (63,69). Polymeric acetylated xylan can be isolated from delignified materials by dimethyl sulfoxide extraction (70). The choice of substrate is especially important in studies of esterases for deacetylation of xylans. The use of small chromophoric substrates (p-nitrophenyl acetate, a-naphthyl acetate, and methylumbelliferyl acetate) analogously to the assays of disaccharidases may lead to the monitoring of esterases unable to deacetylate xylan (33, 63, 64). 

Rhinehart BL, Robinson KM, Payne AJ, Wheately ME, Fisher JL, Liu PS, Cheng W. (1987), Castanospermine blocks the hyperglycemic response to carbohydrates in vivo A result of intestinal disaccharidase inhibition. Life Sci 41 2325-2331. 

Scofield AM, Fellows LE, Nash RJ, Fleet GWJ. (1987) Inhibition of mammalian digestive disaccharidases by polyhydroxy alkaloids. Life Sci 39 645-650. 

Disaccharides are cleaved to monosaccharides by a battery of disaccharidases after absorption into intestinal mucosal cells. 

Source and kinds of disaccharidases The final digestive processes occur at the mucosal lining of the small intestine. Several disaccharidases [for example, lactase (p-galactosidase), sucrase, maltase, and isomal-tase] produce monosaccharides (glucose, galactose, and fructose). These enzymes are secreted by and remain associated with the luminal side of the brush border membranes of intestinal mucosal cells. Absorption of the monosaccharides requires specific trans porters. 

In the mammal, complex polysaccharides which are susceptible to such treatment, are hydrolyzed by successive exposure to the amylase of the saliva, the acid of the stomach, and the disaccharidases (e.g., maltase, invertase, amylase, etc.) by exposure to juices of the small intestine. The last mechanism is very important. Absorption of the resulting monosaccharides occurs primarily in the upper part of the small intestine, from which the sugars are earned to the liver by the portal system. The absorption across die intestinal mucosa occurs by a combination of active transport and diffusion. For glucose, the aclive transport mechanism appears to involve phosphorylation The details are not yet fully understood. Agents which inhibit respiration (e.g., azide, fluoracetic acid, etc.) and phosphorylation (e.g., phlorizin), and those which uncouple oxidation from phosphorylation (e.g., dinitrophenol) interfere with the absorption of glucose. See also Phosphorylation (Oxidative). Once the various monosaccharides pass dirough the mucosa, interconversion of the other... 

Intestinal Disaccharidase Activity The results of the determination of small intestine mucosal maltase and sucrase activity for all animals fed treatment diets for 18 months are given in Table VII. No difference was detected in the activities of these enzymes from the animals fed the instant breakfast product or the hydrolyzed egg albumin. The animals fed the browned egg albumin,... 

The observed decrease in disaccharidase activity is in agreement with earlier published reports 29) The mechanism of... 

Again, the clinical significance of this effect is probably minimal. Although the maltase activity is decreased in rats fed the Maillard browned egg albumin, the activity is still above that found for rats fed either browned or control hydrolyzed egg albumin. In addition, no other clinical consequences of the lowered disaccharidase activity were detected in these animals, such as effects on weight gain or serum glucose levels. 

Alkaline phosphatase, acid phosphatase, 5 -nucleotidase, monoacyl hydrolase, ribonuclease, type 1 phosphodiesterase, adenosine triphosphatase, adenyl cyclase, glycosyl transferase, esterases and disaccharidase have been biochemically or cytochemically demonstrated in the tegument of various cestodes (152, 210, 250, 374, 491, 620, 624-626, 651, 718, 763, 776, 898). Several of these enzymes - phosphatases, 5 -nucleotidase and phosphodiesterase - probably have a digestive and/or absorptive function but the role of the others is uncertain. 

Kumar, G.S., Shetty, A.K. and Salimath, P.V. (2005a) Modulatory effect of fenugreek seed mucilage and spent turmeric on intestinal and renal disaccharidases in streptozotocin induced diabetic rats, journal of Medicinal Food 8(3), 382-385. 

Know the names and modes of action of carbohydrate digestive enzymes found in the saliva and the small intestine, including the amylases and disaccharidases review how glucose and other hexoses are absorbed. 

Biochemical part of the barrier contains alkaline phosphatase, y-glutamytranspeptidase, dipeptidylpep-tidase IV, aminopeptidase N, endopeptidase 24-11 and disaccharidases saccharidase, isomaltase, lactase. Among metabolising enzymes Phase I enzymes CYP 1A1 and 3A4 and Phase II enzymes glutathion-S-transferase, sulfotransferase and glucuronidase are present. 

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