Exploration of some components of fatty acid biosynthesis in prokaryotes and eukaryotes : PANK of homo sapiens and fabl of plasmodium falciparum

Abstract

Coenzyme A (CoA) is a central molecule that plays a key role in this process. In the course of this project, we have attempted to address some key questions that deal with an enzyme involved in CoA biosynthesis (Pantothenate Kinase from Homo sapiens) and in subsequent use of CoA derivatives in the synthesis of fatty acids (Enoyl?ACP reductase or FabI from Plasmodium falciparum). Pantothenate kinase (PANK) is a key regulatory enzyme in the CoA biosynthesis pathway where it catalyzes the first committed step. It phosphorylates pantothenate (vitamin B?) to yield phosphopantothenate that is subsequently processed to give CoA. Four genes encode different isoforms of PANK in humans. Interestingly, mutations in PANK2 have been linked to a neurodegenerative disorder named Pantothenate Kinase Associated Neurodegeneration (PKAN). Although several hypotheses explaining the possible link between PANK2 and PKAN exist, there is still no clear picture of what exactly happens. Thus, the main objective of this project was to study the biochemical and biophysical properties of the wild?type and mutant PANKs (containing mutations in sites known to be clinically relevant) and to interpret the results in light of what is known and what needs to be understood. The fatty acid biosynthetic pathway in P. falciparum is unique in that it is a Type?II fatty acid synthesis (FAS) pathway, like that previously found only in plants, prokaryotes and archaea, and unlike that found in its human host (where Type?I FAS is used). The final reduction step in the fatty acid synthesis is catalyzed by enoyl?ACP (acyl carrier protein) reductase (ENR; also known as FabI) to form acyl?ACP. This is the rate?determining step in the fatty acid biosynthesis and therefore is an attractive target for antimalarials. Triclosan, a common additive found in consumer products like toothpaste and mouthwash, targets FabI and disrupts lipid synthesis in bacteria and causes rapid parasite ablation. In the present study, we characterized mutants that contained a mutation in residues thought to be important for the activity of the enzyme and for binding triclosan. Such studies will enable the rational synthesis of drugs that bind better and lead to stronger inhibition of FabI, thereby leading to more efficient treatment of malaria.