DNA polymerase III holoenzyme. Graphic representation of the complete DNA (deoxyribonucleic acid) polymerase III enzyme. DNA polymerases are enzymes that synthesise new strands of DNA from a complementary template strand during DNA replication. The alpha, epsilon and theta subunits make up the core polymerase enzyme. The beta subunit acts as a DNA clamp. The tau subunits (dark blue) hold the two core enzymes together. The delta, gamma, chi and psi subunits act to load the DNA into the clamp.