The Enzyme Database

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EC 4.4.1.42     
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 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.
Links to other databases: BRENDA, EXPASY, Gene, KEGG, MetaCyc
References:
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. [DOI] [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. [DOI] [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) . [DOI] [PMID: 33567250]
[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)]
 
 


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