Intestinal Maltase

L. Sim, K. Jayakanthan, S. Mohan, R. Nasi, B. D. Johnston, B. M. Pinto, and D. R. Rose, New glucosidase inhibitors from ayurvedic herbal treatment for type 2 diabetes Structures and inhibition of human intestinal maltase-glucoamylase with compounds from Salacia reticulata, Biochemistry, 49... 

Kotalanol Salacia oblonga (Celastraceae) Rat intestinal maltase sucrase... 

Valiolamine (89), an aminocyclitol produced by Streptomyces hygroscopicus var. limoneus, is a potent inhibitor of pig intestinal maltase and sucrase, with IC50 values of 2.2 and 0.049 pM, respectively [107]. Numerous iV-substituted valiolamine derivatives were synthesized to enhance its a-glucosidase inhibitory activity in vitro and the very simple derivative voglibose (90), which is obtained by reductive amination of valiolamine with dihydroxyacetone, was selected as the potential oral antidiabetic agent [108]. Its IC50 values toward maltase and sucrase were 0.015 and 0.0046 pM, respectively. Voglibose (the brand name Basen) has been commercially available for the treatment of type 2 diabetes in Japan since 1994. 

Adjacent to the mucosa, no agitation is possible and the transport rate of most drugs is determined by passive diffusion in the aqueous medium. The thickness of the layer in situ amounts to about 500 pm and in vitro to about 150-200 pm. The average unstirred layer thickness can be calculated from Michaelis-Menten constant and maximal velocity of maltose hydrolysis by intestinal maltase. In... 

Introduction of an OH group at the C-6(3 position in hyacinthacine B5 15 to give hyacinthacine C4 23 increased its inhibitory potential toward rat intestinal maltase and amyloglucosidase. 

An enzyme which acts on maltose to produce glucose. Salivary amylase is present in saliva, and intestinal maltase is present in intestinal juice. 

Maltase accompanies amylase in animal tissues and completes the hydrolysis of polysaccharides. It is present in many bacteria, fungi, and yeasts, and in an insoluble form in ungerminated cereals. The optimal range of activity is about pH 6T (intestinal maltase) to pH 4-1 (malt-extract maltase). 

Miglitol (Glyset) is another a-glucosidase inhibitor, but in contrast to acarbose, mightol is systemically absorbed prior to its activity in the small intestine. It also appears to inhibit the enzymes sucrase and maltase to a greater extent than does acarbose. It does not undergo metabolism and is renally excreted unchanged. 

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. 

Digestion of dietary glycogen and starch in the human body begins with the salivary and pancreatic amylases, which cleave a-1,4 linkages at random. It continues with a glucoamylase found in the brush border membranes of the small intestine where it occurs as a complex with maltase.74 Carbohydrases are discussed in Chapter 12, Section B. 

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,... 

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