Derived from carbamic acid (NH2COOH). Carbamates can also inhibits many enzymes whose catalytic active site contains a nucleophilic Serine. This serine can be carbamylated. The first naturally occurring carbamate discovered was physostigmeine( eserine). Many carbamates were developped as insecticides or nerve agents (inhibitors of cholinesterases) but also in medicine. Polymers whose units are joined by divalent carbamate groups NH(C=O)O are an important family of plastics, the polyurethanes.