SALIVARY APYRASE IN AFRICAN AND NEW-WORLD VECTORS OF PLASMODIUM SPECIES AND ITS RELATIONSHIP TO MALARIA TRANSMISSION

The salivary gland activities of apyrase, an enzyme that prevents plat elet aggregation by eliminating ADP, were compared among five members of the Anopheles gambiae species complex and An, albimanus. Within the An. gambiae group, An. quadriannulatus exhibited the lowest amount of enzyme activity at all pH levels measured. Apyrase activity could be separated into three groups at pH 7.5 and 8.0. The two most anthropoph ilic species (An. gambiae and An, arabiensis) exhibited higher activit y at pH 9.0. Anopheles merus and An. melas, both saltwater taxa, and A n. albimanus, a New World species, exhibited peak apyrase activity at pH 8.0. When the effects of divalent cations (Ca(++), Mg(++)) on enzym e activity were compared at pH 8.5, apyrase activity in the presence o f Mg++ could be separated into three levels. Anopheles gambiae and An. quadriannulatus exhibited reduced activity in the presence of Mg++. A nopheles arabiensis, An. merus, and An. melas displayed the highest re lative levels of activity. Anopheles albimanus, with a Mg:Ca ratio of 0.80, was most similar to An. arabiensis. These biochemical difference s suggest that different isoenzymes of apyrase have developed within t he genus Anopheles.