Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.26 (invertase)
 4,927 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Pig duodeno-jejunal mucosa was maintained in organ culture for up to 24 h in Eagle's minimum essential medium containing 10% foal serum. Viability was controlled by determination of alkaline phosphatase and sucrase activity in the tissue. [14C]Leucine incorporation into proteins decreased 3-fold between 2 and 24 h. Newly synthesized secreted proteins were analyzed by SDS-polyacrylamide gel electrophoresis of the whole culture medium. Apolipoprotein A-I specifically measured by immunoelectrophoresis represented 10-20% of newly secreted proteins. Only 10% of apolipoprotein A-I secreted was recovered with the lipoprotein fraction (d less than 1.21). Recombination of the medium with porcine lipoproteins or DMPC vesicles prior to ultracentrifugation allowed, respectively, the recovery of 40 and 80% of apolipoprotein A-I secreted. The lipoprotein fractions also contained some apolipoproteins B and C and, after DMPC recombination, an apolipoprotein of Mr 45 000, most likely apolipoprotein A-IV, representing about 3.5% of newly secreted proteins. The d greater than 1.21 fractions all contained a high Mr protein, identified as IgA, and an unidentified protein of Mr approximately 45 000. The addition of colchicine (125 microM) to the culture medium did not significantly modify either tissue enzyme activities or [14C]leucine incorporation. It reduced total secretion by about 40% between 2 and 8 h of incubation, without interfering with apolipoprotein A-I secretion, which then represented up to 35% of secretion products. This raises the question of the mode of secretion of apolipoprotein A-I, which may be related to the high proportion of its which is secreted free.
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PMID:Synthesis and secretion of apolipoproteins by pig intestinal mucosa in organ culture. Lack of inhibition of apolipoprotein A-I secretion by colchicine. 641 11

Although Caco-2 cells are frequently employed for the study of enterocyte lipid metabolism, variable results have been reported regarding their ability to synthesize and secrete lipids and apolipoproteins. The major goal of this investigation is to examine the capacity of Caco-2 cells to elaborate and secrete lipids, lipoproteins, and apolipoproteins at different degrees of morphological and functional differentiation. Cells were cultured in medium with 5% fetal bovine serum (FBS), on permeable polycarbonate filters from 2 to 30 d in the presence of 14C-oleate or 35S-methionine. Cellular differentiation, as assessed by morphology (light and electron microscopy), transepithelial resistance, free fatty acid flux, and sucrase activity, progressed steadily up to 20 d of culture. Caco-2 cells esterified oleic acid mainly into phospholipids, triglycerides (TG), and smaller amounts of cholesterol esters. Lipid synthesis began as early as 2 d, and TG secretion was enhanced with increased duration of culture. However, very low efficiency of lipid export was observed at all levels of differentiation, reaching a maximum of only 6% of intracellular lipids. VLDL and LDL were the dominant lipoproteins secreted, with HDL comprising < 20% of the total. VLDL secretion increased, while LDL decreased, whereas the lipid composition of lipoproteins varied little with increasing duration of culture. Apoprotein B and A-I synthesis and secretion increased markedly from 11 to 20 d of culture. The ratio of apo B-100/B-48 decreased between 11 and 30 d, consistent with enhanced apo B editing of more mature enterocytes. Taken together, our data suggest that from 20 d of culture, Caco-2 cells are morphologically and functionally mature, capable of lipid esterification, and lipoprotein and apolipoprotein synthesis. However, despite their functional and morphological similarities to mature enterocytes, Caco-2 cells have a very limited lipid export capacity.
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PMID:Lipid, apolipoprotein, and lipoprotein synthesis and secretion during cellular differentiation in Caco-2 cells. 908 Dec 19

Although oxidative stress has been implicated in development of gut pathologies, its role in intestinal fat transport has not been investigated. We assessed the effect of Fe(2+)-ascorbate-mediated lipid peroxidation on lipid synthesis, apolipoprotein biogenesis, and lipoprotein assembly and secretion. Incubation of postconfluent Caco-2 cells with iron(II)-ascorbate (0.2 mM/2 mM) in the apical compartment significantly promoted malondialdehyde formation without affecting sucrase activity, transepithelial resistance, DNA and protein content, and cell viability. However, addition of the oxygen radical-generating system reduced 1) [(14)C]oleic acid incorporation into cellular triglycerides (15%, P < 0.0002) and phospholipids (16%, P < 0.0005); 2) de novo synthesis of cellular apolipoprotein A-I (apo A-I) (18%, P < 0.05), apo A-IV (38%, P < 0.05), and apo B-48 (45%, P < 0.003) after [(35)S]methionine addition; and 3) production of chylomicrons (50%), VLDL (40%), LDL (37%), and HDL (30%) (all P < 0.0001). In contrast, increased total cellular cholesterol formation (96%, P < 0.0001), assayed by [(14)C]acetate incorporation, was noted, attributable to marked elevation (70%, P < 0.04) in activity of DL-3-hydroxy-3-methyl-glutaryl-CoA reductase, the rate-limiting enzyme in cholesterol synthesis. The ratio of Acyl-CoA to cholesterol acyltransferase, the esterifying cholesterol enzyme, remained unchanged. Fe(2+)-ascorbate-mediated lipid peroxidation modifies intracellular fat absorption and may decrease enterocyte efficiency in assembling and transporting lipids during gut inflammation.
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PMID:Iron-ascorbate alters the efficiency of Caco-2 cells to assemble and secrete lipoproteins. 1089 42