IUBMB Enzyme Nomenclature


Accepted name: S-adenosyl-L-methionine lyase

Reaction: S-adenosyl-L-methionine = L-homoserine lactone + S-methyl-5'-thioadenosine

Other name(s): T3p01 (gene name); SAM lyase; SAMase; adenosylmethionine cyclotransferase; S-adenosyl-L-methionine alkyltransferase (cyclizing)

Systematic name: S-adenosyl-L-methionine S-methyl-5'-thioadenosine-lyase (cyclizing; L-homoserine lactone-forming)

Comments: The enzyme was originally described from the yeast Saccharomyces cerevisiae (as EC, though it had not been well characterized. It was also incorrectly described from several bacteriophages as a hydrolase (EC 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.

Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:


1. Mudd, S.H. The mechanism of the enzymatic cleavage of S-adenosylmethionine to α-amino-γ-butyrolactone. J. Biol. Chem. 234 (1959) 1784-1786. [PMID: 13672964]

2. Mudd, S.H. Enzymatic cleavage of S-adenosylmethionine. J. Biol. Chem. 234 (1959) 87-92. [PMID: 13610898]

3. Hausmann, R. Synthesis of an S-adenosylmethionine-cleaving enzyme in T3-infected Escherichia coli and its disturbance by co-infection with enzymatically incompetent bacteriophage. J. Virol. 1 (1967) 57-63. [PMID: 4918233]

4. Studier, F.W. and Movva, N.R. SAMase gene of bacteriophage T3 is responsible for overcoming host restriction. J. Virol. 19 (1976) 136-145. [PMID: 781304]

5. Guo, X., Soderholm, A., Kanchugal, P., S., Isaksen, G.V., Warsi, O., Eckhard, U., Triguis, S., Gogoll, A., Jerlstrom-Hultqvist, J., Aqvist, J., Andersson, D.I. and Selmer, M. Structure and mechanism of a phage-encoded SAM lyase revises catalytic function of enzyme family. Elife 10 (2021) . [PMID: 33567250]

[EC created 2022 (EC created 1965, incorporated 2022, EC created 1972 as EC, modified 1976, modified 2018, transferred 2022 to EC, incorporated 2022)]

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