1979 Volume 86 Issue 6 Pages 1821-1827
Lipase from Geotrichum candidum (ATCC34614) is a glycerol ester hydrolase which has amolecular weight of 55, 000 with about 7 % carbohydrate, displaying a high affinity for triolein. The enzyme was crystallized from more than 2% protein solution without using any salt or organic solvent. The crystals were cross-linked by soaking in 0.37% glutaraldehyde solution (0.1 m acetate buffer solution, pH 5.6). The structure was determined by X-ray diffraction using the isomorphous replacement technique. Two heavy-atom derivatives [K2PtCl4 and UO2(CH3COO)2] were obtained by the soaking method.
The electron density map calculated at 5 Å resolution clearly showed the molecular boundary. A balsa wood model was made on the basis of the 6 Å electron density map. The molecule has an ellipsoidal shape with dimensions of 70 Å × 50 Å × 50 Å. Several columns of density corresponding to α-helix and a few clefts were found in the molecule. The active site is presumably located in the vicinity of one of the Pt sites in the Pt-derivative crystal, judging from the inactivation of the enzyme by K2PtCl4.
