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      Effect of harmaline on rat intestinal brush border sucrase activity.

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      Indian journal of biochemistry & biophysics

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          Abstract

          The effect of harmaline, a plant alkaloid has been studied on rat intestinal brush border sucrase activity. Stimulation of sucrase activity by Na+ was found to be pH-dependent. At neutral pH, 20 mM Na+ stimulated sucrase activity by reducing K(m) by 30%, while at acidic pH (5.2), the activity increased 4-fold compared to Na+-free enzyme. At 1.0 mM, harmaline markedly inhibited (67%) the enzyme activity at pH 5.2 in the absence of Na+. However, inhibition was reduced in presence of 20 mM sodium, whereas 4.0 mM harmaline was required to inhibit the enzyme activity by 65%. In the absence of Na+ ions, harmaline inhibition of sucrase activity was of competitive type, but it changed to non-competitive type in presence of 20 mM Na+ at pH 5.2. Sucrase-harmaline interactions as a function of pH, both in presence and absence of Na+ revealed a shift in pH optima of the enzyme towards a higher pH in presence of 4 mM and 1 mM harmaline respectively. The observed inhibition was reversible in nature and was only partially overcome by sodium, lithium, potassium, cesium, rubidium and ammonium ions. These findings suggest that harmaline also inhibits rat brush border sucrase and that the presence of Na+ site is not a pre-requisite for the inhibition.

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          Author and article information

          Journal
          Indian J. Biochem. Biophys.
          Indian journal of biochemistry & biophysics
          0301-1208
          0301-1208
          Apr 2002
          : 39
          : 2
          Affiliations
          [1 ] Department of Biochemistry, Postgraduate Institute of Medical Education and Research, Chandigarh 160 012.
          Article
          22896899

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