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)

Brush-border membranes prepared from proximal and distal human small intestine were characterized with respect to lipid fluidity, lipid composition, and protein-lipid interactions. Steady-state fluorescence polarization and differential polarized phase fluorometry revealed that the "static" and "dynamic" rotational components of fluidity (assessed by r infinity values of 1,6-diphenyl-1,3,5-hexatriene and r values of 12-anthroylstearate, respectively) were greater in the distal membranes compared with their proximal counterparts. The lipid fluidity of distal brush-border membranes was also greater as measured by excimer/monomer fluorescence ratio intensities of pyrene decanoate. A lower molar ratio of cholesterol/phospholipid in the distal membranes was responsible for these regional fluidity differences. Lipid thermotropic transitions were detected at 26-28 degrees C using 1,6-diphenyl-1,3,5-hexatriene in proximal and distal membranes. Arrhenius plots of p-nitrophenylphosphatase and gamma-glutamyl transpeptidase activities demonstrated breakpoints in the vicinity of the lipid thermotropic transition temperatures (28-30 degrees C), whereas maltase and sucrase yielded a single activity slope over the range of 10-40 degrees C. Moreover, 50 mM benzyl alcohol fluidized proximal brush-border membranes and increased p-nitrophenylphosphatase activity in this membrane. This agent also shifted the phase transition temperature of the membrane and breakpoint temperature of this enzymatic activity from approximately 28 degrees C to 19 degrees C. These findings demonstrate that differences in human small intestinal brush-border membrane lipid fluidity and lipid composition exist between proximal and distal regions of this organ. Furthermore, alterations in fluidity and/or lipid composition modulate p-nitrophenylphosphatase and gamma-glutamyl transpeptidase but not sucrase or maltase activities in these membranes.
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PMID:Protein-lipid interactions in human small intestinal brush-border membranes. 259 11

Experiments were conducted, using a nonspecific lipid transfer protein, to vary the cholesterol/phospholipid molar ratio of rat proximal small intestinal microvillus membranes in order to assess the possible role of cholesterol in modulating enzymatic activities of this plasma membrane. Cholesterol/phospholipid molar ratios from 0.71 to 1.30 were produced from a normal value of 1.05 by incubation with the transfer protein and an excess of either phosphatidylcholine or cholesterol/phosphatidylcholine liposomes for 60 min at 37 degrees C. Cholesterol loading or depletion of the membranes was accompanied by a decrease or increase, respectively, in their lipid fluidity, as assessed by steady-state fluorescence polarization techniques using the lipid-soluble fluorophore 1,6-diphenyl-1,3,5-hexatriene. Increasing the cholesterol/phospholipid molar ratio also decreased alkaline phosphatase specific activity by approximately 20-30%, whereas decreasing this ratio increased this enzymatic activity by 20-30%. Sucrase, maltase, and lactase specific activities were not affected in these same preparations. Since the changes in alkaline phosphatase activity could be secondary to alterations in fluidity, cholesterol, or both, additional experiments were performed using benzyl alcohol, a known fluidizer. Benzyl alcohol (25 mM) restored the fluidity of cholesterol-enriched preparations to control levels, did not change the cholesterol/phospholipid molar ratio, and failed to alter alkaline phosphatase activity. These findings, therefore, indicate that alterations in the cholesterol content and cholesterol/phospholipid molar ratio of microvillus membranes can modulate alkaline phosphatase but not sucrase, maltase, or lactase activities. Moreover, membrane fluidity does not appear to be an important physiological regulator of these enzymatic activities.
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PMID:Cholesterol modulates alkaline phosphatase activity of rat intestinal microvillus membranes. 337 34

Diabetes was induced in rats by administration of streptozotocin. After 90-120 days, one group of chronic diabetic animals was treated with insulin for chronic diabetic animals was treated with insulin for 10 days. The lipid fluidity and composition of microvillus membranes prepared from ileal enterocytes of control, diabetic, and insulin-treated diabetic animals were determined. Lipid fluidity, as assessed by steady-state fluorescence polarization techniques using the probes 1,6-diphenyl-1,3,5-hexatriene, DL-2-(9-anthroyl)stearic acid and DL-12-(9-anthroyl)stearic acid, was decreased in membranes of diabetic animals compared to membranes of control and insulin-treated diabetic membranes. The differences in fluidity resulted from an increased cholesterol content and cholesterol/phospholipid molar ratio in membranes of diabetic animals. The activities of sucrase and alkaline phosphatase were also found to be higher in membranes of diabetic animals. Insulin treatment, however, failed to significantly influence the enzymatic activities of these membranes. These studies, therefore, demonstrate that alterations in the lipid fluidity, lipid composition, and certain enzymatic activities exist in microvillus membranes of enterocytes prepared from chronic streptozotocin-induced diabetic rats. Administration of insulin for 10 days to these animals restored membrane fluidity and lipid composition but not enzymatic activities to control membrane levels.
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PMID:Correction of abnormal lipid fluidity and composition of rat ileal microvillus membranes in chronic streptozotocin-induced diabetes by insulin therapy. 390 76

In experimental diabetes, a number of intestinal brush-border hydrolases and transport systems are stimulated. In this study, we assessed possible effects of diabetes on the composition and membrane fluidity of rat intestinal brush-border membranes that might correlate with these functional changes. We found similar proportions of lipid and protein in the diabetic and control preparations, although there was a considerable increase in total membrane from the diabetic rats, presumably reflecting mucosal hyperplasia. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of membrane protein revealed an increase in the bands corresponding to sucrase-isomaltase, consistent with an increased enzyme activity of sucrase. Membrane lipid analysis revealed only a decrease in fatty acids of the neutral lipid fraction of diabetics--a change that may well have occurred during membrane preparation. 1-6-Diphenyl-1,3,5-hexatriene fluorescence polarization data, obtained as a function of temperature, was similar for the diabetic and control rats, with a three-phase linear model superior to one- and two-phase linear or quadratic models. The overall composition of the intestinal brush-border membrane, unlike other plasma membranes, appears little affected by experimental diabetes.
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PMID:Intestinal mucosa in diabetic rats: studies of microvillus membrane composition and microviscosity. 662 63

Our study emphasizes the effect of gamma irradiation on intestinal cell membrane fluidity and addresses the potential relationships existing between radiation-induced lipoperoxidation, membrane fluidity, and changes in membrane protein activities. Male Wistar rats were exposed to an 8-Gy total body irradiation (60Co source) and studied 1, 4, and 7 days after irradiation (D1, D4, and D7). Membrane enzyme activities and fluorescence anisotropy were determined on small intestinal crude membrane preparations. The supernatants of membrane preparations as well as plasma were used for malonedialdehyde (MDA) quantification. The effect of carbamylcholine on electrical parameters was estimated on distal ileum placed in Ussing chambers. We observed a decrease in fluorescence anisotropy for at least 7 days, an increase in membrane production of MDA at D4, a decrease in membrane enzyme activities at D4, but an amplification of carbamylcholine-induced increase in short-circuit current at D4 and D7. Furthermore, correlations were observed between the 1,6-diphenyl-1,3,5-hexatriene anisotropy coefficient and sucrase activity and between MDA levels and leucine aminopeptidase activity. Thus, total body irradiation induces changes in intestinal membrane fluidity and an increase in lipoperoxidation. These modifications may have an impact on the activity of membrane proteins involved in intestinal function.
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PMID:Potential role of the membrane in the development of intestinal cellular damage after whole-body gamma irradiation of the rat. 1218 26