title: Computational Study of the Degradation of S-Adenosyl Methionine in Water.
abstract: The degradation of S-adenosyl methionine (SAM) to homoserine-γ-lactone (HSL) and methyltioadenine (MTA) in water is studied with MD simulations. The AM1 Hamiltonian is used for the quantum part and the flexible AMBER force field for the H2O molecules. The MD simulations predict the free energy barrier for the degradation reaction to be between 109 and 112 kJ mol-1and an overall gain in free energy of -26 kJ mol-1. The high barrier and the low energy gain of this reaction can be linked to interactions among the carboxylate group of the SAM molecule and solvent H2O molecules, which are not observed on the product side. Hence, the H2O molecules effectively slow down the reaction that otherwise would be much faster.
authors.affiliation: Department of Chemistry, National Tsing Hua University , Hsinchu 30013, Taiwan.
authors.forename: Timm
authors.initials: T
authors.lastname: Lankau
authors.affiliation: Department of Chemistry, National Tsing Hua University , Hsinchu 30013, Taiwan.
authors.forename: Tzu Nung
authors.initials: TN
authors.lastname: Kuo
authors.affiliation: Department of Chemistry, National Tsing Hua University , Hsinchu 30013, Taiwan.
authors.forename: Chin Hui
authors.identifier: http://orcid.org/0000-0003-4947-017X
authors.initials: CH
authors.lastname: Yu