A glucosidases

Acarbose is a nonabsorbable a-glucosidase inhibitor which blocks the digestion of starch, sucrose, and maltose. The digestion of complex carbohydrates is delayed and occurs throughout the small intestine rather than in the upper part of the jejunum. Absorption of glucose and other monosaccharides is not affected. Acarbose is adrninistered orally three times a day and chewed with the first mouthful of food. 

An example of a direct spectrophotometrical assay is the use of synthetic peptide -nitroanilide substrates to determine protease activity. The /)-nitroani1ine group Hberated from the substrates by the protease can be determined spectrophotometricaHy at 410 nm. An example of an indirect (coupled) spectrophotometric assay is the determination of a-amylase using -nitrophenyLmaltoheptaoside. Initially, the substrate is cleaved by the a-amylase and subsequentiy one of the reaction products, -nitrophenyLmaltotrioside, is cleaved by a-glucosidase, hberating -nitrophenyl, a chromophore... 

The first member of this class, acarbose, was introduced in the early 1990s. a-Glucosidase inhibitors slow the intestinal process of carbohydrate digestion by competitive inhibition of the activity of a-glucosidase enzymes located in the brush border of the enterocytes... 

When a-glucosidase activity is inhibited, carbohydrate digestion is prolonged and takes place further along the intestinal tract. This in turn delays and spreads the period of glucose absorption, which reduces the extent of the postprandial rise in blood glucose concentrations. The effectiveness of a-glucosidase inhibitors is dq en-dent on the consumption of a meal rich in complex carbohydrate. 

The a-glucosidase inhibitors, acarbose (Precose) and miglitol (Glyset), lower blood sugar by delaying die digestion of carbohydrates and absorption of carbohydrates in the intestine. 

The a-glucosidase inhibitors are contraindicated in patients with a hypersensitivity to the drug, diabetic ketoacidosis, cirrhosis, inflammatory bowel disease, colonic ulceration, partial intestinal obstruction or predisposition to intestinal obstruction, or chronic intestinal diseases. Acarbose and miglitol are used cautiously in patients with renal impairment or pre-existing gastrointestinal (GI) problems such as irritable... 

Figure 47-9. Schematic pathway of oligosaccharide processing. The reactions are catalyzed by the following enzymes , oligosaccharideiprotein transferase , a-glucosidase I ...

One of the long-standing criticisms of Bis is that the incubation period required in order to confirm a satisfactory sterilization process imposes an undesirable delay on the release of the product. This problem has been overcome, with respect to steam sterilization at least, by the use of a detection system in which a spore enzyme, a-glucosidase (reflective of spore viability), converts a non-fluorescent substrate into a fluorescent product in as little as Ihour. 

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