The cDNA sequence of human NAMPT was amplified by PCR from the pGex-6p-3-hNAMPT plasmid (kindly gifted from Dr Shui-qing YE, University of Missouri). The PCR goods were digested and cloned right into a pET21a+ vector using NdeI and XhoI restriction enzymes. A point mutation was released by the short adjust web page-directed mutagenesis process util