The lysosomal β-hexosaminidases are dimers composed of α and β subunits. β-
Hexosaminidase A (αβ) is a heterodimer, whereas hexosaminidase B (ββ) and S (αα) are
homodimers. Although containing a high degree of amino acid identity, each subunit
expresses a unique active site that can be distinguished by a differential ability to hydrolyze
charged substrates. The site on the β-subunit primarily degrades neutral substrates,
whereas the α-subunit site is, in addition, active against sulfated substrates. Isozyme …