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)

Caco-2 cells, which express spontaneous enterocytic differentiation at confluency, is one of the most relevant in vitro models for the study of differentiation and regulation of intestinal functions. However, these cells are normally cultured in the presence of 15-20% serum which renders extremely complex the identification of the factors involved in the regulation of both proliferation and differentiation. This study has been devoted to the establishment of chemically defined culture conditions which can sustain growth and differentiation of Caco-2 cells. The replacement of serum by ITS (insulin, transferrin, and selenium) allowed for normal structural and functional differentiation of cells as revealed by the establishment of cell polarity and the expression of brush-border membrane enzyme markers (sucrase, maltase, lactase, alkaline phosphatase, gamma-glutamyltransferase, aminopeptidase N, and dipeptidyl-dipeptidase IV), although the levels of sucrase activity were lower in ITS-supplemented medium. Coating petridishes with either type IV collagen or basement membrane proteins (Matrigel) did not improve the differentiation of cells, brush-border membrane enzyme activities being, in fact, lower when the cells were grown on these substrata. When triiodothyronine (T3, 5 x 10(-8) M) was added to the ITS-supplemented medium, disaccharidase and alkaline phosphatase activities were significantly increased while gamma-glutamyltransferase activity was diminished by T3 and stimulated by epidermal growth factor (1.6 x 10(-6) M). On the other hand, hydrocortisone (HC, 10(-6) M) did not modify disaccharidase and peptidase activities. These data clearly show that Caco-2 cells can be maintained in serum-free medium and that this system allows the study of the factors involved in the regulation of the differentiation of enterocyte in vitro.
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PMID:Caco-2 cells cultured in serum-free medium as a model for the study of enterocytic differentiation in vitro. 193 45

A series of proteins (albumin, transferrin, alpha 1-antitrypsin, alpha-fetoprotein and pancreatic oncofetal antigen) and enzymes (gamma-glutamyltranspeptidase, aminopeptidase M, alkaline phosphatase, alpha-glucosidase and protease) was measured in fetal meconium extracts. There were 19 fetuses thought to have cystic fibrosis (CF), 13 with neural tube defects, three with chromosome abnormalities and 19 normal controls, all with gestational ages between 18 and 21 weeks. With the exception of alpha-fetoprotein, all the proteins and enzymes were significantly elevated in the CF meconium extracts. The most definitive indicator of a CF fetus was the albumin concentration, where the mean level was five times that found in the control groups. However, five of 19 fetuses assumed to have CF had albumin in the normal range. In these cases the meconium protease levels were grossly elevated. Furthermore, in the same five fetuses meconium concentration of pancreatic oncofetal antigen, a protein synthesized in the fetal pancreas, was also greatly raised. We suggest that post-mortem examination of a fetus thought to have CF should include measurement of meconium albumin, protease and pancreatic oncofetal antigen.
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PMID:Biochemical analysis of meconium in fetuses presumed to have cystic fibrosis. 242 27

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

We describe a new and unique gastric carcinoma cell line (LIM1839) derived from a young Caucasian male with rapidly progressing disease. The cell line grows with a pleomorphic morphology and has been in continuous culture for more than 3 years. The cells cannot be cloned in semi-solid agar or grown in nude mice despite numerous attempts. The karyotype of the cultured cells is highly abnormal with a large number of structural and numerical changes. Some chromosomes are dicentric and this feature has persisted in this culture. The cells express one of the small-intestinal dipeptidases, aminopeptidase N, but do not express dipeptidyl peptidase IV or the disaccharidases, sucrase isomaltase or maltase glucoamylase. The cells express high levels of EGF receptors and of messenger RNA for insulin-like growth factor II.
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PMID:A new gastric carcinoma cell line (LIM1839) derived from a young Caucasian male. 260 77

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

Urinary excretions of beta 2-microglobulin (beta 2M), N-acetyl-beta-D-glucosaminidase (NAG), alanine aminopeptidase, beta-glucuronidase, acid and neutral alpha-glucosidase as indicators of proximal tubular dysfunction were measured in patients with acute upper and lower urinary tract infection (UTI) and fever of non-renal origin. The sensitivity of beta 2M was 67% and of NAG 49% as assessed in more than 100 episodes of acute pyelonephritis. Combined use of beta 2M and NAG increased the sensitivity to 75%. The degree of beta 2-microglobulinuria and enzymuria was comparable in patients with acute pyelonephritis and fever due to non-renal infections. The excretion of beta 2M and the various enzymes was too variable and unpredictable in individual cases to be useful as diagnostic indicator. In localizing an acute UTI, tests for proximal tubular dysfunction seem to be of no more clinical value than properly measured body temperature.
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PMID:Diagnostic potential of urinary enzymes and beta 2-microglobulin in acute urinary tract infection. 287 89

Atrophy of the small intestinal mucosa is functionally characterized by a reduction in non-electrolyte transport in vivo. In order to elucidate the cellular defect being responsible for this malabsorption, we have studied the Na+-dependent D-glucose accumulation as well as the activities of aminopeptidase M and maltase in brush border membrane vesicles prepared from jejunal self-emptying blind loops and corresponding intestinal segments of sham-operated control rats. Membrane vesicles from atrophic mucosa did not show any differences in D-glucose uptake or in enzyme activities when compared with those derived from normal intestine. Thus it is unlikely that the impaired non-electrolyte absorption in the atrophic mucosa in vivo is due to a defect in cellular transport processes. It is more probable that the functional impairment is the result of the diminished absorptive surface in this pathophysiological condition.
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PMID:[Functional characterization of luminal enterocyte membranes of the small intestine mucosa using isolated brush border membranes]. 288 Apr 30

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

We have observed seven pregnancies at risk for fetal cystic fibrosis where second-trimester amniotic fluid microvillar enzyme activities presented an unusual pattern. Low gamma-glutamyltranspeptidase and borderline alpha-glucosidase values were associated with normal aminopeptidase M and intestinal alkaline phosphatase values. All seven pregnancies went to term; five of the seven infants were affected with cystic fibrosis.
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PMID:An abnormal pattern of amniotic fluid microvillar enzymes signalling fetal cystic fibrosis. 288 81

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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