Cholesterol modulates alkaline phosphatase activity of rat intestinal microvillus membranes.

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