Apicoplast functions

Therefore, that tryptophanyl-tRNA synthetase production in the apicoplast is upregulated (in the chloroquine-induced microarray data) may suggest that this efflux process was made possible (caused) by the apicoplast, the mini bacterium living inside the malaria parasite. Ralph et al. (45) state that it is not yet clear what the key function of the apicoplast is but the organelle is clearly indispensable. Curiously though, parasites cured of their apico-plasts do not die immediately. Rather, they fail to invade new host cells successfully. This suggests that apicoplasts provide some component essential to invasion and or [sic] establishment of the para-sitophorous vacuole in the host cell (46, 47). 

Ralph SA, van Dooren GG, Waller RF, Crawford MJ, Fraunholz, MJ, Foth, BJ, Tonkin, CJ, Roos, DS and McFadden, GI. Tropical infectious diseases metabolic maps and functions of the Plasmodium falciparum apicoplast. Nat. Rev. Microbiol. 2004 2 203-216. 

This indicates that some de novo FA biosynthesis occurs in the apicoplast. It may occur in a discrete compartment or be related to a specific but crucial type of lipid (predominantly C-10 to C-14, as shown by Surolia and Surolia, 2001). This pathway is probably quantitatively minor but appears to be critical to parasite survival. It could be involved in the synthesis of lipids required by the apicoplast or a specific lipid that may be provided to the parasite. A major interest resides in the fact that FAS II is structurally and functionally distinct from the equivalent pathway in the vertebrate host, and would explain the susceptibility of the malarial parasite to herbicides targeting the enzyme. It is considered today as a validated target that still needs to be developed into a practical antimalarial. 

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