"In situ" determinations of apparent Km and Vmax of brush border disaccharidases along the villi of normal human jejunal biopsy specimens. A quantitative histochemical study.

In order to characterize lactase/beta-glucosidase and the neutral alpha-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 alpha- and beta-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 alpha-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.