Biological catalysis is dominated by enzymes that are made of protein,
but several distinct classes of catalytic RNAs are known to promote c
hemical transformations that are fundamental to cellular metabolism. I
s biological catalysis limited only to these two biopolymers, or is DN
A also capable of functioning as an enzyme in nature? To date, no DNA
enzymes of natural origin have been found. However, an increasing numb
er of catalytic DNAs, with characteristics that are similar to those o
f ribozymes, are being produced outside the confines of the cell. An a
ssessment of the potential for structure formation by DNA leads to the
conclusion that DNA might have considerable latent potential for enzy
matic function.