TDP1, also known as tyrosyl-DNA phosphodiesterase 1, is involved in repairing stalled topoisomerase l-DNA complexes by catalyzing the hydrolysis of the phosphodiester bond between the tyrosine residue of topoisomerase l and the 3-prime phosphate of DNA. This protein may also remove glycolate from single-stranded DNA containing 3-prime phosphoglycolate, suggesting a role in repair of free-radical meditated DNA double-strand breaks. Recombinant human TDP1, fused to His-tag at C-terminus, was expressed in insect cell and purified by using conventional chromatography techniques.