Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.20 (alpha-glucosidase)
 4,237 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The hydrolysis of maltose and maltotriose at the same catalytic site of glucoamylase-maltase has been demonstrated. Maltitol acts as a competitive inhibitor, Ki = 69 (+/-10) mM, of the maltose hydrolysis and as a noncompetitive inhibitor of the hydrolysis of maltotriose, Ki = Kii = 29 (+/-4) mM, and maltotetraose, Ki = Kii = 30 (+/-3) mM. Maltobionate was not hydrolyzed by the enzyme and did not influence the maltose hydrolysis. In contrast, in hydrolysis of maltooligosaccharides it acts as an uncompetitive inhibitor. For the hydrolysis of maltotriose, Kii = 25(+/-8) mM, and maltotetraose, Kii = 30(+/-4) mM was found. According to a characteristic of this rare inhibition pattern a simultaneous decrease of the apparent Km and the apparent Vmax of maltooligosaccharide hydrolysis with increasing maltobionate concentrations was observed. We were able to discriminate two different binding modes for glucoamylase-maltase. Maltitol binds to the free enzyme (maltose binding mode) as well as to the maltooligosaccharide-enzyme complex, whereas maltobionate binds only to the oligosaccharide-enzyme complex (oligosaccharide binding mode). This could be shown by the different inhibition behaviors of maltitol and maltobionate depending on the substrate: maltose or maltooligosaccharides.
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PMID:Maltitol and maltobionate act differently on maltose- and maltooligosaccharide hydrolysis by human small intestinal glucoamylase-maltase indicating two different enzyme binding modes. 861 18

The existence of disaccharidases and an enzyme that hydrolyzes maltitol were investigated in the large intestine of rats. In addition, the properties of disaccharidases were studied in the cecum and colon with hyperplasia induced by the ingestion of nondigestible carbohydrates such as maltitol and glucomannan. Maltase activity was detected in the cecal and colonic mucosa of rats fed a regular diet, although it was a very low level as compared with that in the small intestinal mucosa. Maltitol hydrolysis was notably lower in the cecum and colon than in the small intestine. The Km of maltose was 5.56 mM in the small intestine and 5.59 mM in the cecum, while that in the colon was 2.56 mM. The Vmax of maltose was at very low levels in the cecum (0.38 mumol/mg protein/h) and colon (0.37 mumol/mg protein/h) in comparison with that in the small intestine (30.3 mumol/mg protein/h). With regard to the maltitol hydrolyzing enzyme, Km and Vmax were 2.00 mM and 2.51 mumol/mg protein/h in the small intestine, respectively. Km and Vmax in the cecum and colon could not be measured because the level was too low. The tissue weights of the cecum and colon increased significantly in both the maltitol (p < 0.01, p < 0.05) and glucomannan (p < 0.01, p < 0.05) groups in comparison with that of the control group. The specific activity of maltase decreased significantly in the small intestine of the maltitol (p < 0.05) and glucomannan (p < 0.01) groups. However, maltase activity in the cecum and colon was not lowered by maltitol ingestion, although it decreased significantly in the cecum of the glucomannan group (p < 0.01). Sucrase activity in the small intestine and cecum was decreased significantly by maltitol (p < 0.05, p < 0.01) or glucomannan (p < 0.01, p < 0.01) ingestion, whereas it was not decreased in the colon. Maltitol hydrolyzing activity did not decrease significantly in the small intestine of the maltitol group, although that in the cecum and colon was not measured exactly by the methods used here. These results demonstrate that disaccharidases exist in the cecal and colonic mucosa of rat, and that they are not induced even in the tissue with hyperplasia, which is caused by maltitol ingestion.
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PMID:Disaccharidase activity in rat cecum and colon with hyperplasia induced by maltitol or glucomannan. 959 Dec 35