The beta 2 subunit of human placenta hexosaminidase (Hex) A and B is a non-random association of the two polypeptides beta a and beta b.

The subunit structures of placental Hex A and B have previously been assigned as alpha beta 2 and 2 beta 2, respectively. The beta 2 subunit is composed of two non-identical polypeptide chains, beta a and beta b. Purified Hex A and B were fractionated on a chromatofocusing column, and the fractions were reduced and then alkylated with iodo-1-14C-acetamide. The polypeptide chains were separated by polyacrylamide-gel isoelectric focusing. From the radioactivity measurements of the polypeptides a constant value for beta a/beta b was obtained in all the chromatofocusing fractions, demonstrating a non-random structure of (beta a beta b) in each beta 2 subunit.