Abstract: Parasitic protozoa, a group of unicellular eukaryotes, are pathogens that can cause disease in both human and animal, resulting in serious risk to public health and livestock industry development.DNA helicases, an important class of DNA repair enzymes, are involved in the DNA metabolism of almost all organisms.At present, the research of protozoal DNA helicase mainly focuses on Plasmodium falciparum, the reported DNA helicases of protozoa are mostly homologs of human or yeast, however, their conserved motifs are different from those of human and yeast, and it is an important potential target for studying drugs against protozoa.In this paper, we reviewed the conservative domain and functional characteristics of classical helicases, introducing the biochemical properties of each helicase such as polarity and preferred substrate, summarizing the families of reported DNA helicases of protozoa.At present, most of the reported DNA helicases are concentrated in Plasmodium falciparum.There are 18 species of Plasmodium falciparum, 3 species of Leishmania, 2 species of Trypanosoma brucei and Encephalitozoon cuniculi, and 1 species of Toxoplasma gondii.We also presented the progress of functional studies of the more interesting DNA helicases in protozoa:The RecQ family, DEAD-box family, UvrD family and RuvB family, among which three Plasmodium-specific helicases, PfPSH1/H2/H3 in the DEAD-box family had not found analogues in the host human.Furthermore, UvrD, shows no any homology to Homo sapeins, Mus musculus and Caenorhabditis elegans, and has significant similarity with bacteria and fungi.In this study, we reviewed the basic properties and functions of protozoan DNA helicases, described the current progress of research on protozoan DNA helicases and their potential as drug targets, in order to provide new research ideas for the screening of anti-protozoal drug targets and the prevention and control of protozoal diseases.

Key words: parasitic protozoa; DNA helicase; biological function