"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.
D000328:Adult; D000368:Aged; D002462:Cell Membrane / Q000201:enzymology*; D005260:Female; D005696:Galactosidases / Q000378:metabolism*; D005959:Glucosidases / Q000378:metabolism*; D006801:Humans; D007583:Jejunum / Q000201:enzymology*; D007700:Kinetics; D008297:Male; D008871:Microvilli / Q000201:enzymology*; D008875:Middle Aged; D012044:Regression Analysis; D012737:Sex Factors; D000519:alpha-Galactosidase / Q000378:metabolism*; D000520:alpha-Glucosidases / Q000378:metabolism*; D001617:beta-Glucosidase / Q000378:metabolism*
D005696:Galactosidases; D005959:Glucosidases; D000520:alpha-Glucosidases; D001617:beta-Glucosidase; D000519:alpha-Galactosidase