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

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 Vmax-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 Km-values could be detected. Equally the ratios between the Vmax-values of the disaccharidases remained constant. Male persons exhibited significantly greater apparent Vmax-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.