DNA polymerases of anucleated cells. Isolation and characterization of two DNA polymerases from human platelets

Two different DNA polymerases have been purified and characterized from human platelets. In the mitochondrial fraction a unique activity of the polymerase gamma type has been found. The same enzyme is found in the extramitochondrial supernatant. A second DNA polymerase, called 'cytoplasmic' DNA polymerase has been found in the 10000 x g supernatant of human platelets. The following properties of the latter DNA polymerase from human platelets are identical to those of DNA polymerase alpha from normal cells: DEAE-cellulose and phosphocellulose chromatography, size, thermal stability, phosphonoacetic acid and ethidium bromide inhibition. However, some of its properties, like high resistance to N-ethylmaleimide and the lack of DNA polymerization using synthetic RNA primers, are those of DNA polymerase beta.