The Influence of Three Analogs of Isoleucine on in Vitro Growth and Protein Synthesis of Erythrocytic Forms of Plasmodium Knowlesi ∗

Summary

On the basis that L-isoleucine is essential for in vitro growth of erythrocytic forms of P. knowlesi and that the same amino acid is more avidly incorporated into plasmodial protein than 17 other amino acids; three antagonists of L-isoleucine: L-O-methylthreonine (L-OMT), alloisoleucine and N-acetylisoleucine were examined for their in vitro effect on DNA and protein synthesis of erythrocytic forms of P. knowlesi. L-OMT inhibited markedly and L-alloisoleucine slightly the incorporation of orotic-6-¹⁴C acid into DNA. The inhibitory effect of L-OMT was reversed by L-isoleucine. L-Alloisoleucine and N-acetyl-L-isoleucine did, while L-OMT probably did not compete with isoleucine for incorporation into plasmodial protein. The L-isoleucine antagonists are proposed as a possible new class of antimalarial drugs.