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 β- -galactosidase, β- -glucuronidase, α- -mannosidase, β-NAc- -glucosaminidase and β-NAc- -galactosaminidase activities. Tumoral tissue showed higher β- -galactosidase, β-NAc- -glucosaminidase, and β-NAc- -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 Vmax in tumoral colon with respect to the control for β- -galactosidase, β-NAc- -glucosaminidase, and β-NAc- -galactosaminidase activities. The Km remained unaltered. Conclusions: The increased Vmax 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.