Fidelity of catalysis

Can we create new mutant enzymes with altered fidelity of catalysis and tolerance on non-natural substrates ... 

DNA replication and RNA transcription in what way, at the molecular level, does Mn(II) alter the specificity and fidelity of catalysis of these processes Such questions may only be answered by X-ray crystallographic studies or rapid kinetic approaches to elucidate structural details, along with stepwise changes brought about by substitution of Mn(II) for other divalent ions. 

---