The gene for hypoxanthine phosphoribosyl transferase of Plasmodium falciparum complements a bacterial HPT mutation

The enzyme hypoxanthine phosphoribosyl transferase of Plasmodium falciparum has been overexpressed in Escherichia coli. The protein was found to be active enzymatically. When the recombinant expression vector (pPfPRT2) was transformed and expressed in a Salmonella typhimurium mutant KP1684 (purE deoD hpt gpt), the active expressed protein complemented the hpt mutation in the bacteria. We discuss the practical value of this strain. Assays of the expressed protein in the mutant extract showed that the enzyme is able to use hypoxanthine, guanine and xanthine as substrates. A specificity study using the competitive inhibitor, 6-thioguanine, showed that of these hypoxanthine is the most favourable substrate. The biological significance of xanthine utilisation by the enzyme is discussed.