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Vitamin B 1  (thiamine) is an essential cofactor for several key enzymes of carbohydrate metabolism. Mammals have to salvage this crucial nutrient from their diet to complement their deficiency of  de novo  synthesis. In contrast, bacteria, fungi, plants and, as reported here,  Plasmodium falciparum , possess a vitamin B 1  biosynthesis pathway. The plasmodial pathway identified consists of the three vitamin B 1  biosynthetic enzymes 5-(2-hydroxy-ethyl)-4-methylthiazole (THZ) kinase (ThiM), 4-amino-5-hydroxymethyl-2-methylpyrimidine (HMP)/HMP-P kinase (ThiD) and thiamine phosphate synthase (ThiE). Recombinant  Pf ThiM and  Pf ThiD proteins were biochemically characterised, revealing  K  m  app  values of 68 μM for THZ and 12 μM for HMP. Furthermore, the ability of  Pf ThiE for generating vitamin B1 was analysed by a complementation assay with  thiE -negative  E. coli  mutants. All three enzymes are expressed throughout the developmental blood stages, as shown by Northern blotting, which indicates the presence of the vitamin B 1  biosynthesis enzymes. However, cultivation of the parasite in minimal medium showed a dependency on the provision of HMP or thiamine. These results demonstrate that the human malaria parasite  P. falciparum  possesses active vitamin B 1  biosynthesis, which depends on external provision of thiamine precursors.

biological chemistry

Vitamin B 1  de novo  synthesis in the human malaria parasite  Plasmodium falciparum  depends on external provision of 4-amino-5-hydroxymethyl-2-methylpyrimidine