In addition to polymerase activity, this DNA polymerase exhibits 5'-3' exonuclease activity. a 2'-deoxyribonucleoside 5'-triphosphate + DNA(n) = diphosphate + DNA(n+1) Optimum temperature is 65 degrees Celsius. Single-chain monomer with multiple functions. The enzyme from this organism does not have any 3'-5' exonuclease activity. The subtilisin large fragment (residues 289-876) has wild-type polymerase activity but no 5'-3' exonuclease activity. Belongs to the DNA polymerase type-A family. PubMed:9016716 and PubMed:9440698 strain is not known and has been termed 'X' in this entry.