Alterations of glycosidases in human colonic adenocarcinoma

Objectives: We have carried out a detailed study of some glycosidases in an attempt to explain the differential profile of enzyme activity between human colonic adenocarcinoma and normal mucosa. Design and Methods: Several glycosidase activities associated with human colonic adenocarcinoma and control tissues were submitted to a detailed structural and functional characterization. Results: Tumoral and control samples were assayed for beta-D-galactosidase, beta-D-glucuronidase, alpha-D-mannosidase, beta-NAc-D-glucosaminidase and beta-NAc-D-galactosaminidase activities. Tumoral tissue showed higher beta-D-galactosidase, beta-NAc-D-glucosaminidase, and beta-NAc-D-galactosaminidase activities than control tissue. Glycosidases from tumoral and control tissues demonstrated no differences in optimum pH, subcellular distribution, pH and thermal stability. However, the kinetic analysis showed a statistically significant increased V-max in tumoral colon with respect to the control for beta-D-galactosidase, beta-NAc-D-glucosaminidase, and beta-NAc-D-galactosaminidase activities. The K-m remained unaltered. Conclusions: The increased V-max detected for some glycosidase activities in human colonic adenocarcinoma could correspond with a greater presence of enzyme proteins in the tumoral cells, and not to changes in protein and/or active site structure.