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

1. Trehalase, sucrase-isomaltase and maltase-glucoamylase are three integral glycoproteins of the brush border membranes of the enterocytes. On the basis of a comparative study on alpha-glycosidase activities (sucrase, isomaltase, maltase, glucoamylase and trehalase) associated to these glycoproteins during neonatal development, mammals could be basically divided into three groups. 2. In rodents and rabbit alpha-glycosidase activities are low or undetectable during the suckling period and increase to adult levels during the weaning period. In cat, dog and the primates examined, alpha-glycosidase activities are well or fully developed at birth. 3. In ruminants and pinnipedia alpha-glycosidases are low or absent throughout life. 4. During the suckling period of rat, mouse and rabbit, glucocorticoids trigger a premature and dramatic increase of all alpha-glycosidases. 5. On the contrary, alpha-glycosidases development during the weaning period appears to be independent of glucocorticoids. Neither hypophysectomy nor adrenalectomy prevent the development of alpha-glycosidases; only the rate of increase is reduced. 6. Transplantations of intestinal isografts either in adult or suckling animal, have shown that (1) no systemic factor inhibits the expression of alpha-glycosidase, (2) alpha-glycosidases induction is neither triggered by luminal alimentary substances, nor by hormones, (3) alpha-glycosidase development is controlled by an intrinsic ontogenic program. 7. The use of an antiglucocorticoid failed to inhibit the spontaneous development of alpha-glycosidase activities. 8. The increase of maltase and sucrase activities triggered by glucocorticoids is associated with an increase of the concentration of two glycoproteins in the microvillous membrane: sucrase-isomaltase and maltase-glucoamylase. 9. After administration of glucocorticoids the increase of maltase, sucrase and trehalase is strongly inhibited by actinomycin-D and the increase of sucrase activity is associated with a parallel increase of sucrase-isomaltase mRNA. Transcription is most likely the primary site of control of alpha-glycosidase biosynthesis. 10. In the crypt cells, alpha-glycosidases biosynthesis appears to be triggered by a receptor-mediated glucocorticoid interaction. 11. The enterocytes synthesize more alpha-glycosidase molecules as they travel to the tip of the villi. 12. The simultaneous, biosynthesis of sucrase-isomaltase and maltase-glucoamylase triggered by glucocorticoids, as well as their simultaneous normal development suggest that they may be subjected to related control mechanisms. 13. It is suggested that sucrase-isomaltase and maltase-glucoamylase might have arisen by several cycles of partial gene duplication of an ancestor gene coding for a single site maltase-isomaltase; subsequent mutation would have transformed isomaltase into sucrase or glucoamylase.
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PMID:Brush border membrane sucrase-isomaltase, maltase-glucoamylase and trehalase in mammals. Comparative development, effects of glucocorticoids, molecular mechanisms, and phylogenetic implications. 251 62

1. Brush border membrane vesicles were prepared from lamb enterocytes. These were used to study the changes in the enzyme contents and the transport capacities which occur during the change from a milk to a roughage diet. 2. Na+-dependent transport of D-glucose was present in all regions of the small intestine of pre-ruminant lambs and absent in ruminants. 3. Na+-dependent transport of L-proline was present in all regions of the small intestine irrespective of the age of the animal. 4. Phosphate transport was seen only in the presence of a transmembrane pH gradient (acid outside). The transport was not stimulated by either Na+ or K+. The transport capacity increases 2-fold as the animal becomes ruminant. 5. The activities of lactase and maltase diminished with age. Alkaline phosphatase and aminopeptidase N activities remain constant. Sucrase activity cannot be detected in lambs of any age.
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PMID:Changes in the functions of the intestinal brush border membrane during the development of the ruminant habit in lambs. 251 73

The influence of glucocorticoid administration and limited nursing on piglet carbohydrase enzyme development and subsequent growth was examined in three experiments using 371 piglets. Treatments in the first two experiments were formed by the factorial arrangement of hydrocortisone (-HYD or +HYD) and limited nursing (-LN or +LN) imposed form d 14 to weaning (d 28). Hydrocortisone was replaced by adrenocorticotropic hormone (ACTH) in the third experiment. Growth rates were severely depressed by HYD (P less than .01), LN (P less than .001) and to a lesser extent (P less than .06) by ACTH during the last 2 wk of lactation. During the first 14 d postweaning, piglets continued to grow more slowly following HYD treatment (P less than .01), whereas LN piglets grew more rapidly than those allowed to suckle normally. Although piglets were smaller at weaning after HYD injection (P less than .01), relative weights of liver, pancreas and small intestine were increased (P less than .05). Only adrenal weights were increased by ACTH (P less than .09). Pancreatic and intestinal amylase activities were increased two- to three-fold by HYD injection (P less than .05) but were unaffected by ACTH or LN (P greater than .10). Sucrase and maltase activity increased linearly with age (P less than .001). This rate of increase was numerically enhanced by glucocorticoid treatment and LN. The normal decrease in lactase activity was accelerated by LN and HYD injection, with the greatest depression caused by the combination of LN and either HYD or ACTH administration (P less than .05). Glucocorticoid administration to nursing piglets can evoke premature elevation of the carbohydrase enzymes necessary for initiating the hydrolysis of starch.
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PMID:Effect of glucocorticoids and limiting nursing on the carbohydrate digestive capacity and growth rate of piglets. 255 55

Starch is the main carbohydrate in the food of poultry. Starch granules are digested by pancreatic alpha-amylase in the small intestine. Intestinal villi have enterocytes that project microvilli with a fibrous glycocalyx from the surface. These fine structures are envisaged to entrap water that is mixed with mucin from nearby goblet cells to form the "unstirred water layer." Maltose, maltotriose and alpha-limit dextrins must diffuse across this first barrier to absorption to be hydrolyzed by maltase and sucrase-isomaltase immobilized at the membrane; however, the resultant glucose, once formed, accrues at the surface to provide a concentration advantage. Fowl adjust to changes in dietary starch by altering the amount of amylase released, intestinal surface area and enterocyte carbohydrase concentration. Enterocytes arising during embryonic development have no carbohydrases and are not involved with glucose absorption, but they appear to be specialized for maternal immunoglobin transfer in ovo. Embryonic villi are stimulated by transfer activity, and their growth depends on enterocytes arising from the crypt. Mature crypt cells are capable of digestion-absorptive activities and dominate the villus shortly after the chick hatches when yolk sac reserves are depleted.
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PMID:Digestion and absorption of carbohydrates in fowl and events through perinatal development. 258 3

The synthesis and secretion of apolipoprotein B (apo B) was studied in a human colon carcinoma (Caco-2) cell line and in explants from normal human intestine. In Caco-2 cells, the specific activity of the intestinal disaccharidases maltase, sucrase-isomaltase and lactase was enhanced 8-, 6- and 3-fold respectively, at 19 days post-confluence as compared with 1-day-post-confluence cultures. The level of apo B secreted into the medium increased from undetectable in the cells just reaching confluency, to 115 ng/ml at 18 days post-confluence. The presence of apo B-100 and apo B-48 with mobilities on SDS/polyacrylamide-gel electrophoresis corresponding to those of human very-low-density lipoproteins and lymph chylomicrons, respectively, was detected in the media from 7-, 12- and 18-days-post-confluence cells. These two apo B proteins were also found intracellularly in 7-day-post-confluence cultures. However, more differentiated cells (12 and 18 days post-confluence) accumulated large amount of a 214 kDa protein intracellularly. Apo B-related 214 kDa protein was also synthesized by normal human intestinal explants. A pulse-chase experiment with explants from normal human jejunum showed a slow intracellular conversion of the 214 kDa protein into the size of mature apo B-48 (264 kDa), concomitant with increasing amounts of mature apo B-48 in the medium, suggesting a precursor-product relationship. Despite large intracellular quantities, the 214 kDa protein from the normal human tissue and Caco-2 cells was absent from the medium. No apo B-100 synthesis was detected in the human explants. These findings may help in our understanding of cholesterol and lipid metabolism in health and in some disorders characterized by the inability to secrete apo B-containing lipoproteins.
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PMID:Biosynthetic precursor (214 kDa) of apolipoprotein B-48 is not secreted by Caco-2 cells and normal human intestine. 260 23

An experiment was done to determine maltase, sucrase, isomaltase, and trehalase activities in mucosa of different segments of small intestines of young turkeys as influenced by age and diet. Two-day-old poults were fed diets containing no added fat [44.6% starch, 2.2% ether extract by weight (HC)], 10% tallow (T), or 10% corn oil [(CO) 29.0% starch, 10.9% ether extract]. Diets HC, T, and CO were calculated to contain 2,705, 3,083, and 3,196 kcal ME/kg, respectively, and constant protein, TSAA, and lysine:ME ratios were maintained. Appreciable maltase and isomaltase specific activities (micromoles of substrate hydrolyzed per milligram protein per hour) were observed in 2-day-old poults, and activities of these enzymes increased in poults fed the HC diet through 7 and 14 days, respectively. At 2 days, specific activity of sucrase was low, and trehalase activity was not detected. Sucrase activity increased steadily through 28 days of age in poults fed the HC diet. Trehalase activity was detected at 7 days of age and reached a maximum by Day 21 after hatch. By Day 28, trehalase activity had disappeared from all segments except for the proximal jejunum. In 28-day-old poults fed the HC diet, specific activities of all disaccharidases were greatest in the jejunal segments; i.e., 21, 1.06, 7.24, and .034 mumol/mg protein/h for maltase, sucrase, isomaltase, and trehalase, respectively, in the proximal jejunum. Poults fed the T or CO diets had significantly lower disaccharidase activities than did those fed the HC diet, beginning at 7 days of age. Changes in specific activities of disaccharidases as related to age or diet or both were not always parallel, suggesting that each enzyme may be regulated by or affected by diet in a partly independent way.
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PMID:Intestinal disaccharidases of young turkeys: temporal development and influence of diet composition. 264 74

We report the relative frequency of sucrase-isomaltase (SI) antigen expression in human colonic adenocarcinoma (22/57), in peritumoral mucosa taken next to the tumor (31/41) or distant from it (29/42) as well as in 21/23 polyps. Our results are based on indirect immunofluorescence with a monoclonal antibody (MAb) specific for human intestinal SI. A regular and intense expression of SI occurred only in 6 tumor specimens. In the remaining 16 SI-positive tumor samples, labelling was heterogeneous, i.e., scattered over more or less extensive areas. A similar irregular staining pattern was also found in polyps and in peritumoral mucosa, irrespective of its distance from the tumor. Electron microscopic examination of 19 carcinomas mostly revealed altered brush-border membrane features, irrespective of histological SI staining pattern. Brush-border enzyme activities of sucrase, alkaline phosphatase and maltase showed no difference between tumor specimens and peritumoral mucosa, but aminopeptidase was depressed in the former. Sucrase activity was extremely low (mean values 1.1 to 1.8 mU/mg protein) and rose only exceptionally to 17.5 mU/mg prot.
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PMID:Sucrase-isomaltase expression and enterocytic ultrastructure of human colorectal tumors. 275 30

The "high-mannose" glycosylated forms of aminopeptidase N (EC 3.4.11.2), maltase-glucoamylase (EC 3.2.1.20), and sucrase-isomaltase (EC 3.2.1.48, EC 3.2.1.10) have been purified. The high-mannose glycosylated form of sucrase-isomaltase was found to have a lower specific activity than the complex glycosylated form, whereas no difference was observed for the two other enzymes. The change in glycosylation from high-mannose to complex form thus seems to be of importance for the enzymatic activity of sucrase-isomaltase either by direct structural involvement or by a general stabilization effect on the protein conformation.
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PMID:Enzymatic activity of "high-mannose" glycosylated forms of intestinal microvillar hydrolases. 286 40

Castanospermine, an inhibitor of glucosidase I, the initial enzyme in the trimming of N-linked carbohydrate, was used to study the importance of carbohydrate processing in the biosynthesis of microvillar enzymes in organ-cultured pig intestinal explants. For aminopeptidase N (EC 3.4.11.2), aminopeptidase A (EC 3.4.11.7), sucrase-isomaltase (EC 3.2.1.48-10) and maltase-glucoamylase (EC 3.2.1.20), castanospermine caused the formation of novel transient forms of higher Mr than corresponding controls, indicating a blocked removal of glucose residues. For the first three enzymes, the 'mature' (Golgi-processed) forms were similar in size to or slightly smaller than corresponding controls and were, as shown for aminopeptidase N, endoglycosidase-H-sensitive, evidence of a blocked attachment of complex sugars. Maltase-glucoamylase did not undergo conversion into a 'mature' form, suggesting that, unlike other microvillar enzymes, it does not receive post-translational O-linked carbohydrate. Castanospermine suppressed the synthesis of the four enzymes, but did not block their transport to the microvillar membrane, showing that processing of N-linked carbohydrate is not required for microvillar expression. The proteinase inhibitor leupeptin partially restored the suppressed synthesis, indicating that the majority of the wrongly processed enzymes, probably because of conformational instability, become degraded soon after synthesis rather than being transported to the microvillar membrane.
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PMID:Biosynthesis of intestinal microvillar proteins. Processing of N-linked carbohydrate is not required for surface expression. 288 40

The behaviour of several enzymes is described of the fetal chick duodenum in tissue culture in a defined medium free of serum and hormones. During culture the activity of sucrase, maltase, alanine aminopeptidase, and gamma-glutamyltransferase is raised in tissue explants, whereas the activity of other enzymes (dipeptidyl peptidase IV, leucine amino-peptidase, alkaline phosphatase) remains constant. After culture, depending on the enzyme, a varying amount of activity is found in the medium, a part of which can be sedimented by ultracentrifugation. Sucrase is subject to the strongest increase in activity during culture and thus should represent a sensitive marker for investigating maturation processes in the fetal intestine and their disturbances.
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PMID:Behaviour of several enzymes of fetal chick intestine in tissue culture. 290 97


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