Thermolabile exonucleases

A method of nucleic acid amplification, said method comprising:

• (a) amplifying nucleic acid by a nucleic acid amplification reaction selected from the group consisting of a polymerase chain reaction (PCR), a ligase amplification reaction (LAR), a strand displacement amplification (SDA), a nucleic acid sequence based amplification (NASBA) and a loop-mediated isothermal amplification (LAMP) to produce a nucleic acid amplification product after a final amplification step of the nucleic acid amplification reaction and
• (b) subsequently contacting the nucleic acid amplification product with an exonuclease under conditions which permit the digestion of at least a portion of any single stranded DNA present in the nucleic acid amplification product and optionally then heating the mixture to inactivate said exonuclease,
• wherein said exonuclease has the amino acid sequence of SEQ ID NO:1 or an amino acid sequence which is at least about 85% identical thereto, wherein said exonuclease
• (i) is at least 90% irreversibly inactivated by heating at a temperature of about 55° C. for 10 mins in a buffer consisting of 10 mM Tris-HCl, pH 8.5 at 25° C., 50 mM KCl and 5 mM MgCl2;
• (ii) has activity against double stranded DNA that is equal to or less than 15% of its activity against an equivalent amount of single stranded DNA under the same assay conditions;
• and
• (iii) has a 3′-5′ exonuclease activity.