Characterization and crystallization of recombinant human cathepsin L.

Human procathepsin L (25mg) was highly purified from the culture filtrate (4L) of mouse myeloma cells (Sp-HCL/HE14) transformed with human procathepsin L cDNA. The procathepsin L was almost completely converted to the mature form (18mg) under the acidic condition. Some properties of the mature cathepsin L were found to be different from those of the human liver-derived enzyme. In addition, we first produced crystals of mature human cathepsin L with E-64 using polyethylene glycol 6000 as the precipitant. The crystal was orthorhombic and belonged to the space group P2(1)2(1)2(1). The unit cell dimensions were: a = 49.8 A, b = 103.9 A, c = 47.8 A. The cell volume (2.47 x 10(5) A3) and calculated molecular mass (24.6 kDa) gave a volume/mass ratio of 2.5 A3/Da, which indicates that the asymmetric unit contains one molecule of enzyme.