ZINC (ZN2-I BUT NOT GROUP-II PHOSPHOLIPASE A(2)() BINDS TO AND STIMULATES THE ACTIVITY OF GROUP)

Phospholipase A(2) plays an important part in the generation of inflam matory lipid mediators and so it is of major interest to understand fu nctional distinctions between structurally similar forms of phospholip ase A(2). in the present study, the influence of zinc (Zn2+) on the ac tivity of group I and group II phospholipase A(2) was examined in vitr o. It appeared that Zn2+ (0.04-1 x 10(-3) M) increased group I phospho lipase A(2) activity from porcine pancreas and rat lung whereas the ac tivity of group II phospholipase A(2) from Crotalus atrox and Vipera r usselli was unaffected. The presence of Cd2+ of Hg2+ (0.8-5 x 10(-3) M ) also increased group I pancreatic phospholipase A(2) activity while no augmentation was found with Cr2+, Fe2+ or Mg2+. The selective stimu lation of group I phospholipase A(2) by Zn2+ corresponded to a binding of these phospholipases A(2) to a zinc-affinity column, while group I I phospholipase A(2) was not bound. Furthermore, the PLA(2) activity i n bronchoalveolar lavage fluid from rat was stimulated by Zn2+. These results indicate that Zn2+ binds to and increases the activity of grou p I, but not group II phospholipase A(2). This difference in Zn2+-bind ing may be used to discriminate between group I and group II phospholi pase A(2) and to separate the enzymes from each other in complex biolo gical materials. The possibility that activation of group I phospholip ase A(2) in the lung is important in zinc-induced metal fume fever is implied.