We used a combined computer and biochemical approach to characterize human pyridoxine 5¢-phosphate oxidase (PNPO).The human PNPOgene is composed of seven exons and six introns, and spans approximately 8 exon/intron junctions contain the gt/ag consensus splicing absence of TATA-like sequences, the presence of Sp1-binding sites and more importantly, the presence of CpG islands in the regulatory region of thePNPOgene are characteristic features of housekeeping genes.