In the past, several unsuccessful attempts have been made to dissociate homodimeric enolases into their active monomeric forms. The main objective of these studies had been to understand whether intersubunit interactions are essential for the catalytic and structural stability of enolases. Further motivation to investigate the properties of monomeric
enolase has arisen from several recent reports on the involvement of
enolase in diverse nonglycolytic (moonlighting) functions, where it may occur in monomeric form. Here, we report successful dissociation of dimeric enolases from Plasmodium falciparum, yeast and rabbit muscle into active and isolatable monomers. Dimeric enolases could be dissociated into monomers by high concentrations ( approximately 250 mm) of
imidazole and/or
hydrogen ions. Two forms were separated using Superdex-75 gel filtration chromatography. A detailed comparison of the kinetic and structural properties of monomeric and dimeric forms of recombinant P. falciparum
enolase showed differences in specific activity,
salt-induced inhibition and inactivation, thermal stability, etc. Furthermore, we found that enolases from the three species differ in their dimer dissociation profiles. Specifically, on challenge with
imidazole, Mg(II) protected the enolases of yeast and rabbit muscle but not of P. falciparum from dissociation. The observed differential stability of the P. falciparum
enolase dimer interface with respect to mammalian enolases could be exploited to selectively dissociate the dimeric parasite
enzyme into its catalytically inefficient, thermally unstable monomeric form. Thus
enolase could be a novel therapeutic target for
malaria.