Nature uses 20 amino acids to make diverse proteins. However, since the diversity from 20 amino acid — Physical Chemistry — Kinetics Chemistry Question

Nature uses 20 amino acids to make diverse proteins. However, since the diversity from 20 amino acids sometimes is not enough, chemical modifications are carried out mostly at the side chains of amino acids to generate more diverse functional groups by many natural enzymes. Many types of these post–translational modifications are important in recognition of protein–protein, protein–DNA, protein–RNA molecules. These modifications are used as turn–on (off) switches, transferring messages, known as signal transduction in living cells. Recently, methylation was found to be as important as other known post–translational modifications, such as phosphorylation and glycosylation. Like other modifications, there is a reverse reaction, demethylation. The two processes work oppositely, turning signals on and off (off and on), like phosphorylation and glycosylation. However, processes of methylation and demethylation in nature are quite different. In other words, the mechanisms of the two facilitating enzymes are not the reverse of each other.