Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

Expression and cellular localization of brush-border enzymes (aminopeptidase N, dipeptidylpeptidase IV, lactase, maltase) in normal human colon, colonic polyps and malignant intestinal tumors were investigated with a panel of monoclonal antibodies reacting with either native or denatured proteins. The enzymes were detected on cryostat sections by indirect immunofluorescence staining, or affinity-purified and analyzed by gel electrophoresis and immunoblotting. Dipeptidylpeptidase IV, lactase and maltase were absent from all samples examined, while aminopeptidase N (APN) was detected at the basal membrane of the epithelial cells in most specimens of colon obtained from individuals free of intestinal tumors. In contrast, APN was frequently localized at the luminal membrane of the surface epithelium in large-intestinal mucosa distal to tumors, adenomas and hyperplastic polyps, and from members of hereditary colon cancer syndrome families. APN was also expressed in colonic tumors, where it was present in an apical cell membrane location in 3/23 adenomas and 14/35 adenocarcinomas examined. No correlation was found between tumor-cell invasiveness (classified by "Dukes" stage) and expression or cellular location of aminopeptidase N. Histologically, all positive tumors were moderately or well differentiated. These results suggest that aminopeptidase N is normally expressed in adult human colon, but epithelial cells in the large and small intestine differ in their ways of sorting this enzyme intracellularly and eventually inserting it into different aspects of their surface membrane, a process which may be altered at an early stage of carcinogenesis.
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PMID:Expression and different polarity of aminopeptidase N in normal human colonic mucosa and colonic tumors. 137 88

A panel of monoclonal antibodies was produced against purified microvillus membranes of human small intestinal enterocytes. By means of these probes three disaccharidases (sucrase-isomaltase, lactase-phlorizin hydrolase, and maltase-glucoamylase) and four peptidases (aminopeptidase N, dipeptidylpeptidase IV, angiotension I-converting enzyme, and p-aminobenzoic acid peptide hydrolase) were successfully identified as individual entities by SDS PAGE and localized in the microvillus border of the enterocytes by immunofluorescence microscopy. The antibodies were used to study the expression of small intestinal hydrolases in the colonic adenocarcinoma cell line Caco 2. This cell line was found to express sucrase-isomaltase, lactase-phlorizin hydrolase, aminopeptidase N, and dipeptidylpeptidase IV, but not the other three enzymes. Pulse-chase studies with [35S]methionine and analysis by subunit-specific monoclonal antibodies revealed that sucrase-isomaltase was synthesized and persisted as a single-chain protein comprising both subunits. Similarly, lactase-phlorizin hydrolase was synthesized as a large precursor about twice the size of the lactase subunits found in the human intestine. Aminopeptidase N and dipeptidylpeptidase IV, known to be dimeric enzymes in most mammals, were synthesized as monomers. Transport from the rough endoplasmic reticulum to the trans-Golgi apparatus was considerably faster for the peptidases than for the disaccharidases, as probed by endoglycosidase H sensitivity. These results suggest that the major disaccharidases share a common biosynthetic mechanism that differs from that for peptidases. Furthermore, the data indicate that the transport of microvillus membrane proteins to and through the Golgi apparatus is a selective process that may be mediated by transport receptors.
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PMID:Expression and intracellular transport of microvillus membrane hydrolases in human intestinal epithelial cells. 389 50

The expression of small intestinal hydrolases associated with the enterocyte brush border membrane was studied in human colon cancers and foetal colons, by means of monoclonal antibodies against human small intestinal sucrase-isomaltase (SI), maltase-glucoamylase (MGA), lactase (L), aminopeptidase N (APN), and dipeptidylpeptidase IV (DPP-IV). The enzymes were visualized by indirect immunofluorescence on cryostat sections of tumors developed in nude mice with 6 human colon carcinoma cell lines (HT-29, Caco-2, SW-480, HRT-18, HCT-8R, and Co-115), of 27 primary colorectal carcinomas from patients, and of human foetal (16 to 20 weeks of gestation) and normal adult small intestines and colons. All 5 monoclonals bound to the brush border of the adult small intestine, but not to that of the adult colon mucosa. Antibodies against SI, APN and DPP-IV also bound to the brush border of the foetal colons, to apical borders in HT-29 and Caco-2 tumors in nude mice, and to brush border-like structures in 7/27 tumors from patients. No binding was observed for MGA and L in either tumors or foetal colons. Binding of anti-SI antibodies to the brush border of the juxta-tumoral mucosal epithelium was observed in 9/11 samples tested. These data indicate that some colon tumors exhibit a typical pattern of enterocytic differentiation which is of foetal type and which involves at least 3 brush border membrane hydrolases. Monoclonal antibodies to small intestinal hydrolases may, therefore, be important tools for identification and characterization of some differentiated colonic tumors.
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PMID:Immunohistological evidence, obtained with monoclonal antibodies, of small intestinal brush border hydrolases in human colon cancers and foetal colons. 638 73

Human intestinal angiotensin-converting enzyme (ACE) exists in the brush-border membrane as a monomeric protein of apparent molecular mass 184 kDa. It is associated with the membrane via a hydrophobic segment and has a transmembrane orientation [Naim (1992) Biochem. J. 286, 451-457]. In addition to the membrane-bound form (ACEm), hydrophilic forms of ACE (ACEsec) can be identified in biosynthetically labelled intestinal cells. Thus the culture medium of biosynthetically labelled human biopsy samples contains an ACE molecule which has an apparent molecular mass similar to that of its membrane-bound counterpart. The secreted ACEsec forms follow a precursor/product relationship with the mature ACE molecule. The effect of the monomeric structure of ACE in its intracellular transport and secretion was investigated by pulse-chase experiments on human biopsy samples labelled with [35S]methionine. The results reveal 2-3-fold slower transport of ACE from the endoplasmic reticulum (ER) to the Golgi as compared with the homodimeric proteins dipeptidylpeptidase IV and aminopeptidase N. Further, the transport kinetics of ACE are comparable with those of human sucrase-isomaltase and human maltase-glucoamylase, two brush-border disaccharidases that do not form homodimers in the ER of human small-intestinal cells. These findings strongly suggest that homodimerization of brush-border proteins may influence the rate of transport of these proteins from the ER to the Golgi. The effect of glycosylation on the transport and secretion of ACE was investigated by utilizing several inhibitors of glycan processing. Here, secretion of ACE molecules continued to take place, albeit to a considerably lesser extent. In fact, approx. 2-fold less ACE molecules were secreted in the presence of inhibitors of ER glucosidases I and II and cis-Golgi mannosidase-I, suggesting that carbohydrate processing is important in the attainment of a transport-competent conformation.
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PMID:Human small intestinal angiotensin-converting enzyme: intracellular transport, secretion and glycosylation. 828 58

The development of hydrolase activity in the intestinal brush border membrane is important for the maturation of digestive function in early life. The development and glucocorticoid control of intestinal enzymes were investigated in the mink (Mustela vison), a carnivorous species, in which the intestine matures relatively late in postnatal life. Mink kits (n = 110 from 20 litters) were either not treated or injected intramuscularly for 7 d with saline, adrenocorticotropic hormone [ACTH, 50 micrograms/(kg.d)] or cortisol 21-acetate [synthetic glucocorticoid, 50 mg/(kg.d)]. The kits were killed at 2, 4, 6, 8 or 10 wk of age and the proximal, middle and distal intestine removed for analyses. Lactase activity was maximal at 4 wk and decreased to about 5% of this level during the following 2 wk. Cortisol treatment stimulated total lactase activity at 2 wk (170% that of controls, P < 0.05) and reduced this activity at 4 wk (20% that of controls, P < 0.001). Aminopeptidases N and A underwent their major developmental increases in activity at 4-6 wk and again, enzyme development was stimulated by cortisol. Other enzymes showed either a gradual increase (maltase), a slight decrease (dipeptidylpeptidase IV) or no consistent change (sucrase) in activity with advancing age from 2 to 10 wk, but the activities remained highest in cortisol-treated kits. Treatment with ACTH enhanced the activity of all enzymes at 2 wk but had little effect thereafter. Intestinal hydrolases develop later in the mink and are sensitive to glucocorticoid induction for a longer period in postnatal life than in species such as rats, pigs or humans. The mink is a useful model in studies of the regulatory mechanisms which influence the development of intestinal brush border hydrolases.
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PMID:Intestinal hydrolytic activity in young mink (Mustela vison) develops slowly postnatally and exhibits late sensitivity to glucocorticoids. 881 92

Maturation of the fetal gastrointestinal tract (GIT) is influenced by both luminal stimuli (e.g. swallowed fluid) and hormonal factors (e.g. endogenous cortisol release). The aims of the present study were 1) to investigate GIT growth and maturation during the last 20% of gestation in pigs (term = 114 +/- 2 d), and 2) to investigate the effect of esophageal ligation, to prevent fetal swallowing, at 80% to 91% gestation. In normal fetuses, marked increases occurred during late gestation in body weight (+95%), relative intestinal weight (+79%, g kg(-1) body weight), activity of some digestive enzymes (1.5- to 10-fold), and absorption of glucose and intact proteins (3- to 6-fold). Fetuses with ligated esophagi had lowered body weight (-20%), reduced intestinal weight (-43%), aminopeptidase A activity (-24%), and glucose absorption (-27%), while lactase, sucrase, and dipeptidylpeptidase IV activities were increased (+40-50%), compared with sham-operated fetuses (all p < 0.05). Other parameters of GIT function remained unchanged by esophageal obstruction (absorption of amino acids and immunoglobulin, activity of chymosin, amylase, trypsin, chymotrypsin, maltase, aminopeptidase N -- all expressed per gram GIT tissue). Ligated fetuses had elevated cortisol levels, which is known to stimulate fetal GIT maturation. We conclude that the rapid development of GIT function in late gestation is diminished by esophageal obstruction, mainly due to slower GIT growth and not inhibition of normal functional development of enterocytes.
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PMID:Prenatal development of gastrointestinal function in the pig and the effects of fetal esophageal obstruction. 1219 78

For many mammalian species short-term fasting is associated with intestinal atrophy and decreased digestive capacity. Under natural conditions, strictly carnivorous animals often experience prey scarcity during winter, and they may therefore be particularly well adapted to short-term food deprivation. To examine how the carnivorous gastrointestinal tract is affected by fasting, small-intestinal structure, brush-border enzyme activities and hepatic structure and function were examined in fed mink (controls) and mink that had been fasted for 1-10 days. During the first 1-2 days of fasting, intestinal mass decreased more rapidly than total body mass and villus heights were reduced 25-40%. In contrast, tissue-specific activity of the brush-border enzymes sucrase, maltase, lactase, aminopeptidase A and dipeptidylpeptidase IV increased 0.5- to 1.5-fold at this time, but returned to prefasting levels after 6 days of fasting. After 6-10 days of fasting there was a marked increase in the activity of hepatic enzymes and accumulation of intra-hepatic lipid vacuoles. Thus, mink may be a useful model for studying fasting-induced intestinal atrophy and adaptation as well as mechanisms involved in accumulation of intra-hepatic lipids following food deprivation in strictly carnivorous domestic mammals, such as cats and ferrets.
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PMID:Short-term fasting induces intra-hepatic lipid accumulation and decreases intestinal mass without reduced brush-border enzyme activity in mink (Mustela vison) small intestine. 1550 54

Summary Prostasomes are prostate-derived organelles in seminal plasma exhibiting pluripotent properties to facilitate the fertilization process. Seminal prostasome concentration, size distribution and expression of the prostasomal surface antigens CD10, CD13, CD26 and CD59 were examined by flow cytometry. The study group consisted of 79 men with involuntary infertility. Very strong correlations existed between the prostasome expressions of the different CD markers. Significant correlations between prostasome concentration and CD molecules were weak or lacking. Further, no or weak relationships were observed between the prostasomal CD markers and sperm morphology, seminal fructose, neutral alpha-glucosidase activity, zinc and tumour necrosis factor alpha concentrations. Flow cytometry is a practical way to study prostasomes in seminal fluid without prior separation. This is a new technique for evaluation of the role of prostasomes and their functions in male reproductive physiology.
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PMID:Flow cytometric technique for determination of prostasomal quantity, size and expression of CD10, CD13, CD26 and CD59 in human seminal plasma. 1653 55

The main objective of this study was to determine the effect of fiber source and concentration on morphological characteristics, mucin staining pattern, and mucosal enzyme activities in the gastrointestinal tract of pigs. The experiment included 50 pigs from 10 litters weaned at 4 wk of age (BW 8.6 +/- 1.4 kg) and divided into 5 treatment groups. Diets containing fiber of various physico-chemical properties and concentrations were formulated to contain 73, 104, or 145 g of dietary fiber/kg of DM. The diets were based on raw wheat and barley flours. Pectin and barley hulls, representing soluble and insoluble fiber sources, respectively, were used to increase the fiber concentration. The pigs were fed the experimental diets for 9 d, and then the pigs were euthanized and the entire gastrointestinal tract was removed. Tissue samples were taken from the mid and distal small intestine and from the mid colon. Inclusion of pectin in the diets significantly decreased (P < 0.001) ADFI and ADG compared with pigs fed no pectin. The villi and the crypts were shorter in pigs fed pectin-containing diets, but the villous height/crypt depth ratio was unaltered. Pectin significantly decreased the area of mucins in the crypts of the small intestine, indicating that the pigs fed the pectin-containing diet would probably be more susceptible to pathogenic bacteria, although this cannot be separated from the impact on ADFI. The lectin-binding pattern of the intestinal mucosa was unaffected by diet. The activity of lactase and maltase was increased in pigs fed diets with high fiber content, whereas sucrase activity was increased in pigs fed the pectin-containing diets. The activity of the peptidases, aminopeptidase N and dipeptidylpeptidase IV, was increased when feeding high fiber diets, whereas the activity of gamma-glutamyl transpeptidase remained unaffected by the experimental diets. In conclusion, the reduced feed intake observed with the pectin-containing diets could explain the lower villous height and crypt depth observed in this study. However, direct effects of pectin also are possible, and thus further study is warranted. Feeding pigs high insoluble fiber diets improved gut morphology by increasing villi length and increased mucosal enzyme activity when compared with pigs fed pectin-containing diets. The mucin content as determined by staining characteristics suggests that pigs fed high insoluble fiber diets might be better protected against pathogenic bacteria than pigs fed diets high in soluble fiber.
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PMID:Intestinal morphology and enzymatic activity in newly weaned pigs fed contrasting fiber concentrations and fiber properties. 1669 94

The intestine of newborn pigs develops rapidly during the first days postpartum. We investigated if feeding milk replacer (infant formula) as an alternative to colostrum has compromising effects on nutrient digestive function in the neonatal period. Nineteen piglets born at term were assigned to one of four treatments: (1) newborn controls; (2) natural suckling for 24 h; (3) tube-fed formula for 24 h; (4) tube-fed porcine colostrum for 24 h. All three fed groups showed significant increases in small-intestinal and colonic weights, villous heights and widths, maltase and aminopeptidase A activities, and decreases in dipeptidylpeptidase IV activity, relative to newborn pigs. Following oral boluses of mannitol, lactose or galactose, formula-fed pigs showed significantly reduced plasma levels of mannitol and galactose compared with colostrum-fed pigs. Activity of intestinal inducible NO synthase and plasma levels of cortisol were significantly increased, whereas intestinal constitutive NO synthase and alpha-tocopherol were decreased in formula-fed pigs compared with colostrum-fed pigs. Although formula-fed pigs only showed minor clinical signs of intestinal dysfunction and showed similar intestinal trophic responses just after birth, as those fed colostrum, lactose digestive capacity was markedly reduced. We conclude that formula-feeding may exert detrimental effects on intestinal function in neonates. Formula-induced subclinical malfunction of the gut in pigs born at term was associated with altered NO synthase activity and antioxidative capacity.
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PMID:Formula-feeding reduces lactose digestive capacity in neonatal pigs. 1676 28


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