These are opposed to isozymes, which are enzymes that perform the same function, but which are coded by genes located at different loci.
[1] Alloenzymes are common biological enzymes that exhibit high levels of functional evolutionary conservation throughout specific phyla and kingdoms.
They are used by phylogeneticists as molecular markers to gauge evolutionary histories and relationships between different species.
As expected DNA polymerase shows relatively small differences in its amino acid sequence between phyla and even kingdoms.
The less well conserved the enzyme is, the more amino acid differences will be present in even closely related species.