T7 Exonuclease acts in the 5' to 3' direction, catalyzing the removal of 5' mononucleotides from duplex DNA

T7 Exonuclease is able to initiate nucleotide removal from the 5' termini or at gaps and nicks of double-stranded DNA. It will degrade both 5' phosphorylated or 5' dephosphorylated DNA. It has also been reported to degrade RNA and DNA from RNA/DNA hybrids in the 5' to 3' direction but is unable to degrade either double-stranded or single-stranded RNA. The protein is the product of T7 gene 6.