Pyridoxal-5'-phosphate phosphatase (PLPP) catalyzes the dephosphorylation of pyridoxal-5'-phosphate (PLP). A human brain PLPP gene was fused with a PEP-1 peptide and produced a genetic in-frame PEP-1-PLPP fusion protein. The purified PEP-1-PLPP fusion protein was efficiently transduced into PC12 cells in a time- and dose-dependent manner when added exogenously to culture media. Once inside the cells, the transduced PEP-1-PLPP fusion protein was stable for 36 h. The concentration of PLP was markedly decreased by the addition of exogenous PEP-1-PLPP to media pretreated with the vitamin B(6) precursors; pyridoxine, pyridoxal kinase and pyridoxine-5'-phosphate oxidase into cells. The results suggest that the transduction of the PEP-1-PLPP fusion protein can be one mode of PLP level regulation, and to replenish this enzyme in the various neurological disorders related to vitamin B(6).