CRYSTAL STRUCTURE OF PHOSPHOLIPASE A₂ FROM AGKISTRODON HALYS BLOMHOFFII VENOM. K. Tomoo^1*, M. Doi¹, T. Ishida¹, K. Ikeda², Y. Samejima³, ¹Department of Physical Chemistry, ²Department of Biochemistry, Osaka University of Pharmaceutical Sciences, Japan, ³Institute for Medical Chemistry, Hoshi University, Japan

PhospholipaseA₂ (PLA₂) are calcium-dependent lipolytic enzymes involved in a number of physiologically important cellular processes, such as the inflammatory response through the release of arachidonic acid from the phospholipids in the plasma membrane. The PLA₂ from the venom of Agkistrodon halys blomhoffii (AHB-PLA₂) characteristically reveals its biological activity as a monomer form, whereas many other PLA₂ function as dimmer. In order to understand fully the structure-function relationship in AHB-PLA₂, we studied the X-ray structure analysis of this enzyme.

Crystals of AHB-PLA₂ have been obtained at room temperature using 0.1M Tris-HC1 buffer(pH=8.0) with 5mM CaCl₂ and hexylene glycol as precipitant. Crystal belong to the hexagonal space group P 6₁22 with cell dimensions of a=b=64.4Å,c=172.4Å. The intensity data were collected up to 2.5Å resolution using Rigaku R-AXIS IIC. Initial structure was determined by the method of molecular replacement using a start model of PLA₂ from Crotalus atrox venom . Refinement was carried out using the program X-PLOR. The analysis of the detailed structure is in progress.