T4 nucleotide Poly Kinase, T4 PNK for short, is expressed by E. coli. The source of the expressed gene is T4 bacteriophage. It can catalyze the transfer and exchange of phosphate between the γ-position of ATP and the 5'-hydroxyl end of oligonucleotide chains (double-stranded or single-stranded DNA or RNA) and 3'-monophosphate nucleosides. At the same time, it also has 3' phosphatase activity, which can hydrolyze the 3'-phosphate group from the 3' phosphate end of oligonucleotides, deoxy3'-monophosphate nucleosides and deoxy3'-diphosphate nucleosides. The T4 polynucleotide kinase can be used for 5' end labeling or phosphorylation of oligonucleotides, DNA or RNA, and catalyzing 3' phosphorylation of single nucleotide 5' phosphorylation and removal of 3' end phosphate groups, etc. This product can be inactivated by heating at 75 ℃ for 10 minutes and can also be inactivated by adding EDTA. Metal ion chelators, phosphates, ammonium ions, KCl and NaCl in concentrations greater than 50 mM can significantly inhibit its activity.