PROTEIN ENGINEERING TESTS OF A HOMOLOGY MODEL OF PLASMODIUM-FALCIPARUM LACTATE-DEHYDROGENASE

This paper describes the testing of a homology model of Plasmodium fal ciparum lactate dehydrogenase (pfLDH) by protein engineering, The mode l had been validated in structural terms, It suggests explanations of the unusual properties of pfLDH (compared with all other LDHs), These unusual features are a lack of substrate inhibition, high activity wit h the synthetic coenzyme 3-acetylpyridine adenine dinucleotide (APAD()) and changes in residues at previously conserved positions. pfLDH sh ows several amino acid insertions and deletions in an alignment with p rotein sequences from all other known LDHs, The most notable is a five amino acid insertion into the active-site loop, In addition, a conser ved serine at position 163 is replaced by leucine. The results showed that when the unique pfLDH structural features were engineered into Ba cillus stearothermophilus lactate dehydrogenase, the thermophilic enzy me acquired the properties previously uniquely associated with the mal arial enzyme, We conclude that the homology model of the malarial enzy me is adequate for the prediction of successful redesigns and, in the regions tested, is accurate.