Abstract: Objective To inhibit the expression of pyruvate kinase （PK） mRNA in Giardia lamblia by specific hammerhead ribozyme. Methods The constructed hammerhead-GCV vector （pGCV-PKH） which aims to PK mRNA was electroporated into G. lamblia trophozoites （group A）. Electroporated trophozoites （group B） and normal trophozoites （group C） served as control. Trophozoites in each group were collected at 24, 48, 72 and 96 h post-electroporation, respectively. The concentrations of trophozoites were calculated and the growth curves were constructed. At 24，48，72 and 96 h post-electroporation, mRNA of each group was detected by RT-PCR and realtime PCR, respectively. The PK activity was tested by ultraviolet spectrophotometry. Results The growth curve showed that the growth of trophozoites was considerably depressed after 96 h post-electroporation. RT-PCR result displayed that the specific ribozyme mRNA was detected in group A from 24 h to 96 h post-electroporation. At 24 and 48 h after transfection, the PK mRNA level of group A decreased to 5% （5±0.17） and 8% （8±0.19） of the level in group C, respectively; and the PK activity of group A decreased to 32%（32±0.64） and 38% （38±0.65） of the level in group C. Conclusion PK mRNA expression in G. lamblia has been inhibited by specific hammerhead ribozyme.

Key words: Giardia lamblia, Pyruvate kinase, Hammerhead ribozyme