Over-production of lactate dehydrogenase from Plasmodium falciparum opens a route to new antimalarials

Abstract

Over-production of lactate dehydrogenase (PfLDH) from Plasmodium falciparum from E. coli TG2 cells transformed with a pKK223-3 plasmid containing the wild type gene isolated by Bzik DJ, Fox BA, and Gonyer K (1993) Mol. Biochem. Parasit. 59, 155-166, gave mostly an inactive protein after isolation. Sequencing the N-terminus of the over-produced protein showed that the major product commenced at an internal methionine. Truncation of the protein occurred due to the inappropriate priming from a Shine-Dalgarno (SD) sequence upstream of Met 35. Silent mutations of this SD sequence to remove the purine-rich region allowed over-production of the full length PfLDH up to 15 mg protein l(-1) broth. The purified protein exhibited biochemical properties of an authentic LDH enzyme. However, high activity with 3-acetylpyridine adenine dinucleotide as well as with the natural cofactor, NAD, was also observed. The high-resolution X-ray structure obtained from the recombinant enzyme has provided the opportunity for the development of inhibitors specific to PfLDH.