Lambda Exonuclease, double-stranded specific DNase produced by Escherichia coli upon lambda bacteriophage infection. Lambda exonuclease processively degrades one strand of double-stranded DNA (dsDNA) in the 5’→3′ direction. The preferred substrate is blunt-ended, 5´-phosphorylated dsDNA. Lambda exonuclease has reduced activity on non-phosphorylated DNA, single-stranded DNA and DNA having protruding 5′ single-stranded termini.