S-adenosylmethionine: a 'poor man's coenzyme B12' in the reaction of lysine 2,3-aminomutase.

S-Adenosylmethionine (SAM) and an iron-sulphur centre function in place of adenosylcobalamin. Because of its coenzyme BJike role in this reaction, SAM was originally described by H. A. Barker as ‘A poor man’s adenosylcobalamin’ [4]. The conversion of lysine into P-lysine by lysine 2,3-aminomutase proceeds without exchange of solvent protons with substrate hydrogen, and by the stereochemistry illustrated in Equation 2 [5,6]. The purified Clostridial enzyme is a hexamer of identical subunits that contains [4Fe-4S] clusters and pyridoxal5’-phosphate (PLP), and it is activated by SAM [4,7-91. Lysine 2,3-aminomutase is best purified inside an anaerobic chamber because of its sensitivity to dioxygen, and in the presence of low concentrations of PLP and lysine to protect it from activity losses during purification [9,10]. The biological significance of lysine 2,3-aminomutase includes the production of P-lysine for the biosynthesis of antibiotics