The β₂ subunit of human placenta hexosaminidase (Hex) A and B is a non-random association of the two polypeptides α_a and β_b

The subunit structures of placental Hex A and B have previously been assigned as β_a and β_b, respectively. The β₂ subunit is composed of two non-identical polypeptide chains, β_a and β_b. Purified Hex A and B were fractionated on a chromatofocusing column, and the fractions were reduced and then alkylated with iodo-I-¹⁴C-acetamide. The polypeptide chains were separated by polyacrylamide-gel isoelectric focusing. From the radioactivity measurements of the polypeptides a constant value for β₂ was obtained in all the chromatofocusing fractions, demonstrating a non-random structure of (β₂) in each β₂ subunit.