Structure of human erythrocyte catalase

Catalase (E.C. 1.11.1.6) was purified from human erythrocytes and crystalli zed in three different forms: orthorhombic, hexagonal and tetragonal. The s tructure of the orthorhombic crystal form of human erythrocyte catalase (HE C), with space group P2(1)2(1)2(1) and unit-cell parameters a = 84.9, b = 1 41.7, c = 232.5 Angstrom, was determined and refined with 2.75 Angstrom res olution data. Non-crystallographic symmetry restraints were employed and th e resulting R value and R-free were 0.206 and 0.272, respectively. The over all structure and arrangement of HEC molecules in the orthorhombic unit cel l were very similar to those of bovine liver catalase (BLC). However, no NA DPH was observed in the HEC crystal and a water was bound to the active-sit e residue His75. Conserved lattice interactions suggested a common growth m echanism for the orthorhombic crystals of HEC and BLC.