LAUSR

In the current study, we deal with the crucial role of 5′-deoxyadenosyl radical and water in the mechanism of the conversion of l -lysine into l -β-lysine. The DFT (density functional theory)–B3LYP method coupled with 6-31G(d) basis set has been performed to investigate the optimized structures of transition states ( TSs ) and intermediates ( IMs ) of two processes in water: (i) the attack of 5′-deoxyadenosyl radical to complex PLP- l -lysine and (ii) hydrolysis to liberate l -β-lysine. Meanwhile, M062X/6-311++g(3df,2p) level of theory is applied to compute the relative Gibbs energy ΔG. Procedure (i) has undergone various steps but includes two main structural aziridinyl rings TS2 (ΔG = 4.1 kcal/mol) and TS3 (ΔG = 2.3 kcal/mol). In stage (ii), hydroxy group of water would help to break the bond between β-NH 2 group of l -lysine and PLP better than that of Tyr389. Graphical abstract