The activator of cerebroside sulphatase. Purification from human liver and identification as a protein.

1. A heat-stable activator of human sulphatase A (cerebroside sulphatase) was purified from human liver. It is required for the enzymatic degradation of cerebroside sulphates (sulphatides) in buffers (ionic strength greater than or equal 0.2) with osmolarity in the physiological range. 2) The purification steps involve extraction, acetone precipitation, heat treatment, isoelectric focusing and gel filtration. 3) Based on the definition of a specific activator unit, the purification of the final preparation was approximately 2000-fold over the acetone precipitation and several thousand-fold in the overall procedure. 4) The purified activator migrated as a single protein band when subjected to gel electrophoresis. Its effect was abolished after treatement with pronase E. The apparent molecular weight as determined by gel filtration was 21 500 +/- 1500; the isoelectric point was 4.3. 5) The activating effect of this protein factor and of taurodeoxycholate on cerebroside sulphatase activity was compared on a weight and molar basis.