Crystallization and preliminary crystallographic analysis of a new crystal form of arylsulfatase A isolated from human placenta

Depending on pH, arylsulfatase A exists in solution as a dimer or as an octamer. The enzyme isolated from human placenta was crystallized at pH 5.4 in a new crystal form with space group C2, unit-cell parameters a = 154.0, b = 190.3, c = 112.5 Å, β = 122.4° and four subunits in the asymmetric unit. At pH 6.5–6.7, tetragonal crystals are obtained that are isomorphous to the known crystals of recombinant arylsulfatase A obtained at pH 5.0–5.4. The crystal structure of both forms was determined by the molecular-replacement method. The monoclinic crystals contain octamers of the same type as found in the tetragonal form.