Lesch-Nyhan disease (LND) is a severe and incurable X-linked genetic syndrome caused by the deficiency of hypoxanthine-guanine phosphoribosyltransferase (HPRT), resulting in severe alterations of central nervous system, hyperuricaemia and subsequent impaired renal functions. Therapeutic options consist in supportive care and treatments of complications, but the disease remains largely untreatable. Enzyme replacement of the malfunctioning cytosolic protein might represent a possible therapeutic approach for the LND treatment. Protein transduction domains, such as the TAT peptide derived from HIV TAT protein, have been used to transduce macromolecules into cells in vitro and in vivo. The present study was aimed to the generation of TAT peptide fused to human HPRT for cell transduction in enzyme deficient cells. Here we document the construction, expression and delivery of a functional HPRT enzyme into deficient cells by TAT transduction domain and by liposome mediated protein transfer. With this approach we demonstrate the correction of the enzymatic defect in HPRT deficient cells. Our data show for the first time the feasibility of the enzyme replacement therapy for the treatment of LND.