The human β-galactosidase gene, known as the LacZ gene, encodes a 677 amino acid protein with an optimum functional pH range of 6 to 8. Catalytically active β-galactosidases (β-Gal) is a tetramer of four identical subunits, each with an active site, which can independently catalyze the cleavage of terminal galactose. Monovalent cations have a stimulatory effect on the enzymatic reaction, which likely involves a galactosyl-enzyme complex intermediate. β-Gals are widespread in animals, microorganisms and plants.
