β-Hexosaminidase Isozymes in Human Colonic Carcinoma

Isoelectric focusing of crude extracts demonstrated that human colonic carcinomas contained a higher proportion of β-hexosaminidase B than β-hexosaminidase A, while normal human colonic mucosa contained a higher proportion of the A form of the enzyme. Studies of the isolated isozymes showed that β-hexosaminidase B was more stable to heat and more active at low pH than β-hexosaminidase A. Kinetic studies revealed that the A and B forms of β-hexosaminidase had essentially the same Km and Vmax for ρ-nitrophenyl- N -acetyl-β-d-glucosaminide.