Inhibitory Effect of Oxovanadium(IV), Copper(II), and Zinc(II) Ions on the Activity of an Alpha-glucosidase from a Saccharomyces sp.

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We investigated the in vitro and in vivo effects of metal ions on the activity of an alpha-glucosidase (Saccharomyces sp.). CuSO₄, ZnSO₄, and VOSO₄ significantly inhibited the alpha-glucosidase activity in vitro. Additionally, we examined their effects on the blood glucose level by performing oral carbohydrate tolerance tests in both normal ddY mice and streptozotocin-induced diabetic mice. After oral administration of these three metal compounds, the elevation in the blood glucose levels in mice administered disaccharide (sucrose) was significantly suppressed in comparison with untreated mice. On the other hand, the elevation in the blood glucose levels in mice administered monosaccharide (glucose) was not suppressed when such compounds or a vehicle was administered. The results suggested that some metal ions suppress disacharide digestion probably due to the inhibition of the alpha-glucosidase activity in the epithelium of the small intestine.