We have so far identified homogous genes to cyclic AMP-dependent protein kinase (PKA) catalytic subunit and cyclic GMP-dependent protein kinase (PKG) from Plasmodium falciparum libraries based on sequence analysis. A full-length cDNA clone of the PKA catalytic subunit indicated a sequence closely resembled to a previously identified PKA gene from the rodent malaria parasite, P yoelli. The expression of the PKA catalytic subunit transcripts was shown to be developmentally regulated and predominantly in the asexual erythrocytic-stage parasites under normal physiologic conditions. The level of PKG expression is slightly higher in the asexual stages than the sexual stages. However, the PKG expression is low in comparison to PKA in the stages examined. The effort to express recombinant protein kinases in E. coli to date has yet produced any functionally active kinase for biochemical study in vitro. Currently strategy is to generate antibodies specific to these kinases and to directly examine the potential roles of these kinases and related signalling pathways in P falciparum.
