Antisera were raised to preparations of hexosaminidase isoenzymes A and B purified from human liver. Protein that cross-reacted with the liver hexosaminidase was detected by an antibody-consumption method. A cross-reacting protein with a low molecular weight (20000) was partially characterized and purified from control human liver. This protein is also present in the liver of patients with Tay–Sachs disease or with Sandhoff9s disease. Hexosaminidases A and B gave an immunological reaction of partial identity with the low-molecular-weight protein. The possible identity of the low-molecular-weight cross-reacting protein as a subunit of hexosaminidase is discussed.
