?In situ? determinations of apparent K m and V max of brush border disaccharidases along the villi of normal human jejunal biopsy specimens

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Abstract
In order to characterize lactase/β-glucosidase and the neutral α-glucosidase kinetically in the brush border membrane at different villus sites of normal human jejunal mucosa, a quantitative histochemical study has been carried out on biopsy specimens of patients only suffering from functional disturbances revealing normal mucosal architecture. The apparent V max-values of both α- and β-glucosidases increased significantly from the villus base to the transition zone between medium and apical villus third. During enterocyte maturation on the villus no changes in the apparent K m-values could be detected. Equally the ratios between the V max-values of the disaccharidases remained constant. Male persons exhibited significantly greater apparent V max-values for α-glucosidase than females at both villus measuring positions. The findings can be taken as a starting point for the evaluation of local changes of apparent enzyme-kinetic data under pathological conditions.