Core enzyme
A core enzyme consists of the subunits of an enzyme that are needed for catalytic activity, as in the core enzyme RNA polymerase.
An example of a core enzyme is a RNA polymerase enzyme without the sigma factor. This enzyme consists of only two alpha, one beta, one beta prime and one omega. This is just one example of a core enzyme. DNA Pol I can also be characterized as having core and holoenzyme segments, where the 5'exonuclease can be removed without destroying enzyme functionality.
