Structure and chemistry of 4-methylideneimidazole-5-one containing enzymes

The prosthetic group 4-methylideneimidazole-5-one (MIO) is the catalytic component of the ammonia lyase class of enzymes. This family is responsible for the processing of amino acids in a variety of metabolic pathways through the elimination of ammonia to form unsaturated products. Recently, new chemistry has been attributed to this family with the discovery of MIO-based aminomutases. The mechanism of electrophilic chemistry catalyzed by MIO-based enzymes has been investigated for several decades. Recent X-ray crystal structures of members of the family have provided novel insight into the molecular basis for catalysis and substrate recognition. In addition, the inclusion of aminomutases in natural product biosynthetic pathways has spurned recent advances toward rational engineering and chemoenzymatic applications.