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:3.2.1.26 (invertase)
4,927 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A new technique has been developed for the isolation of membrane vesicles from the vitamin D-deficient and vitamin D-treated chick intestinal brush border membrane. The technique involves removal of nuclei from a low speed pellet by discontinuous sucrose gradient centrifugation. The resulting intact brush borders are then homogenized in 0.5 M Tris and the membrane fragments purified on a glycerol gradient. This preparation represents a 20-fold purification of the brush border marker sucrase. After 1alpha-hydroxyvitamin D3 treatment there is a significant increase in membrane phospholipid phosphorous, an alteration in the fatty acid composition of the phosphatidylcholine fraction of membrane phospholipid, and a decrease in sucrase specific activity.
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PMID:Purification and characterization of chick intestine brush border membrane. Effects of 1alpha(OH) vitamin D3 treatment. 67 42

Twenty-eight Sioux and 29 Saluteaux Indians from a southern and an isolated northern Manitoban community were screened for lactose malabsorption; 55 were also screened for sucrose tolerance. Sixty percent of the subjects were lactose malabsorbers; the incidence increased with age. Lactase deficiency appeared, on the average, between 8 and 15 years of age. About 45% of the subjects were lactose intolerant. Malabsorbers who did not regularly drink milk had the highest symptom scores. The northern subjects consumed significantly more lactose and sucrose than the southern subjects. Two Sioux children were sucrose malabsorbers. It was hypothesized that the significantly greater sucrose consumption by the Saulteaux subjects were responsible for their markedly higher blood glucose curve following the sucrose tolerance tests. Dietary sucrose increases jejunal sucrase activity and the intestinal transport of glucose and fructose. Three of eight children less than 4 years were lactose malabsorbers; hence, medical personnel treating noninjective diarrhea in Indian children should examine for lactase deficiency. It was recommended that vitamin D fortified milk supplements to Indian school children be continued and that the milk be treated so as to reduce abdominal symptoms in the intolerant individuals.
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PMID:Disaccharide consumption and malabsorption in Canadian Indians. 85 12

Intestinal Ca2+ malabsorption has been described in spontaneously hypertensive rats (SHRs), but the molecular basis for this defect is unknown. In this study, we measured intestinal alkaline phosphatase and vitamin D-dependent Ca(2+)-binding protein (calbindin-D9k), two proteins implicated in the active pathway of intestinal Ca2+ absorption. Both proteins were measured in the small intestines of SHRs and their normotensive controls, Wistar-Kyoto rats, before, during, and after development of hypertension (4, 9, 14, 18, and 28 wk of age). At all ages, alkaline phosphatase activity in duodenum (0-6 cm) was decreased by 30-57% (P less than 0.001) and by 47-75% in the 2nd intestinal segment (6-12 cm) (P less than 0.001-0.05). Calbindin-D9k was decreased similarly. The decreases of calbindin were statistically significant (P less than 0.001-0.05) in the duodena at 4, 14, 18, and 28 wk (9-30% decreases) and in the 2nd segment at 4, 14, and 18 wk (38-69% decreases; P less than 0.001-0.005). Decreased calbindin in SHRs was documented in animals from two suppliers. The deficiencies of calbindin-D9k and alkaline phosphatase could not be attributed to malnutrition or to a generalized brush-border defect as indicated by body weights and the intestinal marker enzyme sucrase. Although calbindin-D9k was decreased in young SHRs, the serum 1,25-dihydroxycholecalciferol [1,25(OH)2D3] was increased by 59 and 129% in 4- and 9-wk-old SHRs (P less than 0.001), respectively; by contrast, serum 1,25(OH)2D3 was unchanged or decreased in older SHRs.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Intestinal vitamin D-dependent calbindin-D9k and alkaline phosphatase in spontaneously hypertensive rats. 203 38

Epidermal growth factor (EGF) has been reported to increase intestinal calcium absorption in suckling rats. The mechanism of this effect is unknown, as are the roles of vitamin D-dependent and independent pathways. The present studies were undertaken to investigate the ability of EGF to accelerate the postnatal induction of the vitamin D-dependent intestinal calcium-binding protein, calbindin-D9k. Subcutaneous administration of EGF increased duodenal calbindin-D9k in suckling rats by more than 100% (P less than 0.001). The effect of EGF was not seen in older weaned animals or when EGF was given to suckling rats by gavage. Administration of EGF simulated the changes of normal development. 1) It increased calbindin-D9k, and the effect was greater in proximal than distal duodenum. 2) EGF increased alkaline phosphatase activity to the same extent in proximal and distal duodenum. 3) EGF increased sucrase more markedly in distal than in proximal epithelium. Maximal and half-maximal effects of EGF on each of these proteins were observed at twice daily doses of 0.1 and 0.04 microgram/g BW, respectively. 4) EGF at the maximally effective dose produced a small (30%) but statistically significant (P less than 0.005) increase in serum 1,25-dihydroxyvitamin D. 5) Most importantly, EGF treatment resulted in a 2-fold increase in intestinal 1,25-dihydroxyvitamin D receptors (VDR) in the proximal segments of the small intestine (P less than 0.001). EGF effects on calbindin-D9k and VDR were specific for the intestine, as EGF did not change kidney calbindin-D9k or kidney VDR. Thus, EGF was able to prematurely initiate a complex series of molecular changes that occur during normal development. The mechanism of EGF's action to stimulate calcium absorption appears to involve a maturation effect on the vitamin D-dependent pathway.
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PMID:Epidermal growth factor increases intestinal calbindin-D9k and 1,25-dihydroxyvitamin D receptors in neonatal rats. 254 9

The influence of vitamin D and C deficiency on the kinetic parameters of sucrase and alkali phosphatase activities was studied in the microsomal fraction of the small intestinal mucosa of guinea pigs. It was found that Km values for these enzymes did not depend on the animal providing with these vitamins. Deficiency of one of these vitamins did not influence sucrase activity, however, simultaneous elimination of vitamins D and C resulted in the activity rise by 92%. Alkali phosphatase and Ca-ATPase activities proved to be similarly dependent on providing with vitamin D in the presence of vitamin C in the ration, while in the absence of vitamin C this dependence was not observed.
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PMID:[Enzymatic activity of the microsomal fraction of the mucosa of the small intestine in guinea pigs with vitamin D and C deficiencies]. 296 18

Intestinal brush borders were isolated from vitamin D-3-treated and vitamin D-deficient chicks, and protein topography in the paired preparations assessed by the enzymatic release of four marker hydrolases. Exposure of the brush borders to the protease bromelain resulted in soluble levels of alkaline phosphatase, leucine aminopeptidase, maltase, and sucrase activities from preparations of vitamin D-3-treated birds that were 42%, 75%, 64%, and 56%, respectively, of corresponding activities released in preparations from rachitic chicks. Analyses for recovery of enzyme activity revealed that bromelain treatment selectively inactivated 43% of the alkaline phosphatase activity of brush borders obtained from vitamin D-3-replete birds, and preferentially diminished recovered sucrase activity in preparations from vitamin D-deficient chicks. In additional experiments, brush borders isolated from rachitic birds were treated in vitro with the polyene antibiotic filipin or an equivalent volume of vehicle. Subsequent exposure of such preparations to bromelain resulted in little or no differences in levels of marker hydrolase specific activities released from filipin- or vehicle-treated brush borders. However, analyses of membrane-bound specific activities after treatment of brush border preparations with a range of filipin concentrations, revealed a biphasic inhibition of approx. 30% for both maltase and sucrase, relative to vehicle controls, and a smaller effect on alkaline phosphatase and leucine aminopeptidase.
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PMID:Intestinal brush border hydrolase topography. Effects of vitamin D-3 and filipin. 629 47

Vitamin D3 is known to stimulate the absorption of calcium across the asymmetric intestinal epithelial cells. Efforts to elucidate the mechanism of stimulation of intestinal calcium transport by vitamin D are now focused on evaluating the protein composition and topology of the brush-border membrane and its associated core material. Intestinal brush-border membranes were isolated from vitamin D-replete and vitamin D-deficient chicks. Core material proteins were isolated, by sedimentation, from brush-border membranes which were solubilized with Triton X-100. As determined by polyacrylamide gel electrophoresis, dietary vitamin D3 treatment caused no change in the relative amounts of five major core material proteins with Mr = 101,000, 94,000, 67,000, 42,000 (actin), and 17,000. In contrast, dietary vitamin D3 treatment caused a significant reduction in the levels of two proteins with Mr = 111,000 (sucrase) and 83,000, and an increase in the levels of a protein with Mr = 78,000 (possibly a subunit of alkaline phosphatase). The Mr = 111,000, 83,000, and 78,000 proteins are readily solubilized by Triton X-100 and are located on the extracellular surface of the brush-border membrane, as judged by [125I]diazoiodosulfanilic acid and lactoperoxidase 125I labeling. A significant vitamin D-dependent difference was found with respect to iodination of isolated core material as evidenced by the 125I labeling patterns of the Mr = 42,000 protein (actin). The Mr = 42,000 protein was labeled two to three times more extensively when associated with core material derived from vitamin D-deficient chicks as compared to vitamin D-replete chicks. Increasing the salt concentration (0-125 mM KCl) present during core material isolation from either vitamin D-replete or vitamin D-deficient chicks yields core material actin which is more susceptible to iodination by both [125I]diazoiodosulfanilic acid and lactoperoxidase. This increase in the extent of actin iodination is coupled to a salt-induced decrease in the stability of the core material which is evidenced by a decrease in the percentage of total brush-border membrane actin which is Triton-insoluble. This strongly suggests that the vitamin D-induced decrease in the accessibility of actin to iodination reagents results from a vitamin D-dependent change in the structure of the core material. Collectively, these results implicate a role for dietary vitamin D3 in maintaining a specified composition and topology of both the brush-border membrane proteins as well as its associated cytoskeletal core proteins, which is possibly important for intestinal calcium transport.
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PMID:Vitamin D. Its effect on the protein composition and core material structure of the chick intestinal brush-border membrane. 630 7

The effect of exogenous hypercortisolism and 1,25-dihydroxyvitamin D-3 on small-intestinal calcium and glucose transport in the rat was studied at the level of brush-border membrane vesicles generated from isolated villous cells by a freeze-thaw procedure. At 5 X 10(-5) M extravesicular calcium, initial uptake rates in vesicles prepared from triamcinolone-treated adult rats were decreased by 30% after 5 days. Since calcium ionophore A23187 virtually abolished the difference in calcium uptake, triamcinolone appeared to affect calcium channel density or activity rather than intravesicular binding capacity. Kinetic analysis showed that a decrease in Vmax of a saturable calcium transport system could entirely account for the diminished rate of vesicular calcium uptake. Calcium transport rates could be partially restored by in vivo administration of 1,25-dihydroxyvitamin D-3 at a dosage which did not affect vesicular calcium uptake in control animals. Conversely, sodium-driven glucose accumulation in brush-border vesicles from triamcinolone-treated rats was stimulated by 50-70% after 36 h and appeared insensitive to vitamin D. A specific triamcinolone action on the glucose carrier itself rather than on the driving force of the sodium gradient was indicated by (i) a similar stimulation of glucose transport under equilibrium exchange conditions and (ii) an opposite effect of triamcinolone on sodium-driven alanine transport. The triamcinolone-induced changes in calcium and glucose uptake were not accompanied by a gross alteration of membrane integrity in vitro or by major alterations in vesicular protein composition, intravesicular glucose space and sucrase or alkaline phosphatase activity. The modification of vesicular transport properties is discussed in relation to the vitamin D-antagonized inhibition of intestinal calcium uptake and the stimulation of glucose absorption in response to supraphysiologic amounts of glucocorticoids observed in intact epithelium.
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PMID:Calcium and glucose uptake in rat small intestinal brush-border membrane vesicles. Modulation by exogenous hypercortisolism and 1,25-dihydroxyvitamin D-3. 654 50

To determine which region of the intestinal villus was primarily responsible for calcium uptake and whether cells from the different regions of the villus differed in their response to 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3], we studied cells eluted from the duodenal villus in a sequential fashion at various times after vitamin D-deficient chicks had received 1,25-(OH)2D3. The elution scheme employed removes cells from the villus tip first and cells from the villus base last, as was documented by the distribution of alkaline phosphatase activity, sucrase activity, and cytosolic calcium-binding protein (CaBP) in the eluted fractions. Brush border membrane vesicles (BBMV) were prepared from different fractions of the villus. Calcium uptake was greatest in BBMV from cells eluted from the villus tip and least in those from the villus base. The distribution of calcium uptake and alkaline phosphatase activity in the same BBMV were parallel. After 1,25-(OH)2D3 treatment, cytosolic CaBP was observed in the cells from the villus base by 4 h and in all fractions by 8 h; at all times (from 4-24 h), cells from the villus base contained more cytosolic CaBP than did cells from the villus tip. Alkaline phosphatase activity in BBMV was stimulated in all fractions by 4 h; at all times, alkaline phosphatase activity was greatest in BBMV from cells of the villus tip. In contrast, calcium uptake by BBMV was stimulated 2 h after 1,25-(OH)2D3 administration only in cells from the villus tip and was not stimulated even by 24 h in cells from the villus base. These results indicate that the cellular response to 1,25-(OH)2D3 depends on the location of the cell on the villus and that 1,25-(OH)2D3-stimulated calcium flux across the brush border can be dissociated from 1,25-(OH)2D3-stimulated alkaline phosphatase activity and CaBP production.
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PMID:Differential response of duodenal epithelial cells to 1,25-dihydroxyvitamin D3 according to position on the villus: a comparison of calcium uptake, calcium-binding protein, and alkaline phosphatase activity. 654 95

The effect of vitamin D status on the topography of intestinal cell membranes was studied in isolated brush borders, as well as their purified membranes, by limited proteolysis. Addition of papain to brush borders isolated from vitamin D3-treated and deficient chicks resulted in a differential solubilization of leucine aminopeptidase, maltase, and sucrase activities (114, 195, and 79%, respectively, of appropriate control levels) but not alkaline phosphatase activity. In comparison, proteolysis of purified membranes exhibited vitamin D3- and 1,25-dihydroxycholecalciferol [1,25(OH)2D3]-dependent differences in release of all four marker hydrolases monitored. Calcium uptake studies revealed that preincubation with papain yielded vesicles with a calcium content that was 125% of corresponding native vesicles, in preparations from vitamin D3-treated, as well as deficient birds. Membrane vesicles prepared from 1,25(OH)2D3-treated chicks initially accumulated calcium to a greater extent than those from rachitic birds, but thereafter exhibited a decline in calcium content to basal levels. Preincubation with papain, however, abolished this loss of calcium. The combined results indicate that vitamin D mediates alterations in brush border protein topography and raise the possibility that this action of the seco-steroid might be involved in calcium absorption. However, if vitamin D-stimulated calcium transport across the brush border is dependent on a protein carrier, the molecular entity is not sensitive to inactivation by papain.
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PMID:Vitamin D-mediated alterations in the topography of intestinal brush border proteins: effect of papain on hydrolase release and calcium uptake. 684 6


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