title: Substrate specificity of the Plasmodium falciparum glycosylphosphatidylinositol biosynthetic pathway and inhibition by species-specific suicide substrates.
abstract: The substrate specificities of the early glycosylphosphatidylinositol biosynthetic enzymes of Plasmodium were determined using substrate analogues of D-GlcN(alpha)1-6-D-myo-inositol-1-HPO(4)-sn-1,2-dipalmitoylglycerol (GlcN-PI). Similarities between the Plasmodium and mammalian (HeLa) enzymes were observed. These are as follows: (i) The presence and orientation of the 2'-acetamido/amino and 3'-OH groups are essential for substrate recognition for the de-N-acetylase, inositol acyltransferase, and first mannosyltransferase enzymes. (ii) The 6'-OH group of the GlcN is dispensable for the de-N-acetylase, inositol acyltransferase, all four of the mannosyltransferases, and the ethanolamine phosphate transferase. (iii) The 4'-OH group of GlcNAc is not required for recognition, but substitution interferes with binding to the de-N-acetylase. The 4'-OH group of GlcN is essential for the inositol acyltransferase and first mannosyltransferase. (iv) The carbonyl group of the natural 2-O-hexadecanyl ester of GlcN-(acyl)PI is essential for substrate recognition by the first mannosyltransferase. However, several differences were also discovered: (i) Plasmodium-specific inhibition of the inositol acyltransferase was detected with GlcN-[L]-PI, while GlcN-(2-O-alkyl)PI weakly inhibited the first mannosyltransferase in a competitive manner. (ii) The Plasmodium de-N-acetylase can act on analogues containing N-benzoyl, GalNAc, or betaGlcNAc whereas the human enzyme cannot. Using the parasite specificity of the later two analogues with the known nonspecific de-N-acetylase suicide inhibitor [Smith, T. K., et al. (2001) EMBO J. 20, 3322-3332], GalNCONH(2)-PI and GlcNCONH(2)-beta-PI were designed and found to be potent (IC(50) approximately 0.2 microM), Plasmodium-specific suicide substrate inhibitors. These inhibitors could be potential lead compounds for the development of antimalaria drugs.
mesh_terms: D000217:Acyltransferases / Q000037:antagonists & inhibitors / Q000737:chemistry; D000581:Amidohydrolases / Q000037:antagonists & inhibitors / Q000737:chemistry; D000818:Animals; D002474:Cell-Free System / Q000201:enzymology; D004791:Enzyme Inhibitors / Q000737:chemistry*; D006017:Glycolipids / Q000737:chemistry; D017261:Glycosylphosphatidylinositols / Q000037:antagonists & inhibitors* / Q000096:biosynthesis*; D006367:HeLa Cells / Q000201:enzymology; D006801:Humans; D007294:Inositol / Q000031:analogs & derivatives* / Q000737:chemistry; D008364:Mannosyltransferases / Q000037:antagonists & inhibitors / Q000737:chemistry; D010963:Plasmodium falciparum / Q000201:enzymology*; D013045:Species Specificity; D013379:Substrate Specificity
chemical_list: D004791:Enzyme Inhibitors; C415102:GlcNalpha1-6-myo-inositol-1-HPO4-sn-1, 2-dipalmitoylglycerol; D006017:Glycolipids; D017261:Glycosylphosphatidylinositols; D007294:Inositol; D000217:Acyltransferases; C038660:1-acylglycerophosphorylinositol acyltransferase; D008364:Mannosyltransferases; D000581:Amidohydrolases; C087696:N-acetylglucosaminyl-phosphatidylinositol de-N-acetylase