Diabetes stimulates the functional activity of the intestinal brush border membrane with enhancement of both hydrolytic enzyme activity and membrane transport systems. To determine the mechanism of this effect, we studied the effects of streptozotocin diabetes on the metabolism of one membrane protein, sucrase-isomaltase, which increases its activity in diabetes. The protein was purified and an antiserum prepared. Sucrase-isomaltase from control and diabetic rats was immunologically identical as shown by Ouchterlony double-diffusion analysis of papain-solubilized mucosal proteins. The increase in sucrase enzyme activity in diabetic animals (31.0±1.4 U SEM 5 days after streptozotocin vs. 13.1±1.0 in controls) was the consequence of increased enzyme protein and not an alteration in catalytic efficiency as demonstrated by quantitative immunoprecipitin reactions.
Ward A. Olsen, Helen Korsmo
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