The enzyme was originally described from the yeast Saccharomyces cerevisiae (as EC 2.5.1.4), though it had not been well characterized. It was also incorrectly described from several bacteriophages as a hydrolase (EC 3.13.2.2). Later work has shown the bacteriophage enzyme to be a lyase. The enzyme binds its substrate at the border between two subunits of a trimeric complex in a position that prevents it from interacting with water. Instead, the substrate reacts with itself and splits in two. The product, L-homoserine lactone, spontaneously hydrolyses to L-homoserine.
History
EC 4.4.1.42 created 2022 (EC 2.5.1.4 created 1965, incorporated 2022, EC 3.13.2.2 created 1972 as EC 3.3.1.2, modified 1976, modified 2018, transferred 2022 to EC 3.13.2.2, incorporated 2022)
Synthesis of an S-adenosylmethionine-cleaving enzyme in T3-infected Escherichia coli and its disturbance by co-infection with enzymatically incompetent bacteriophage.
