Klenow fragment,enzyme
A subfragment of DNA polymerase I produced by proteolytic cleavage of the 103 kD enzyme by subtilisin. The Klenow fragment is the larger (68 kD) of the two subfragments produced by subtilisin treatment. This fragment retains the normal DNA polymerase and 3′→5′ exonuclease activities but lacks the 5′→3′ exonuclease of the intact enzyme.