Dihydroorotase of human malarial parasite Plasmodium falciparum differs from host enzyme.

Abstract Plasmodium falciparum , the causative agent of human malaria, is totally dependent on de novo pyrimidine biosynthetic pathway. A gene encoding P. falciparum dihydroorotase ( pf DHOase) was cloned and expressed in Escherichia coli as monofunctional enzyme. Pf DHOase revealed a molecular mass of 42 kDa. In gel filtration chromatography, the major enzyme activity eluted at 40 kDa, indicating that it functions in a monomeric form. This was similarly observed using the native enzyme purified from P. falciparum . Interestingly, kinetic parameters of the enzyme and inhibitory effect by orotate and its 5-substituted derivatives parallel that found in mammalian type I DHOase. Thus, the malarial enzyme shares characteristics of both type I and type II DHOases. This study provides the monofunctional property of the parasite DHOase lending further insights into its differences from the human enzyme which forms part of a multifunctional protein.