The key difference between Klenow fragment and DNA polymerase 1 is that Klenow fragment is a large portion of DNA polymerase 1 which lacks 5′ to 3′ exonuclease activity while DNA polymerase is an enzyme of E. coli which has all three domains including 5′ to 3′ exonuclease activity.
DNA polymerase is one of the key enzymes involved in DNA replication in living organisms. There are different forms of DNA polymerase enzyme found in eukaryotes and prokaryotes based on the size and shape. DNA polymerase 1, 2 and 3 are found only in prokaryotic organisms, and they play different roles in DNA replication. DNA polymerase 1 has three domains with 5′ to 3′ polymerase, 3′ to 5′ exonuclease activity and 5′ to 3′ exonuclease activity. Klenow fragment is a proteolytic product of DNA polymerase 1. It possesses 5 to 3′ polymerase and 3′ to 5′ exonuclease activities of intact DNA polymerase 1, but it lacks the 5′ to 3′ exonuclease activity.
