beta-Hexosaminidases are enzymes involved in the hydrolysis of terminal N-acetyl-D-hexosamine residues in GM2 gangliosides and globo-sphingolipids in lysosomes. The enzymes are composed of two alpha and/or beta subunits, which are coded by HEXA and HEXB genes, respectively. Different associations of the alpha and beta subunits gives rise to beta-hexosaminidase isoforms A, B and S (Hex A, B and S), which have the composition of alpha/beta, beta/beta and alpha/alpha, respectively. Our recombinant HEXA is presumably isoform Hex S, because only alpha subunit was expressed. Hex S is suggested to release non-reducing end N-acetylgalactosamine residues from dermatan sulfate, chondroitin sulfate and sulfated glycolipid SM2. Recombinant HEXA is also highly active on 4-methylumbelliferyl-N-acetyl-beta-D-glucosaminide. Mutations in HEXA and HEXB genes cause lysosomal lipid storage disorders. Specifically, mutations of HEXA cause Tay-Sachs disease, manifested by the harmful accumulation of ganglioside GM2 in tissues and nerve cells in the brain. Children with this disease usually die by age 4.