Biochemical Characterization of an Arginine 2,3-Aminomutase with Dual Substrate Specificity

Summary of main observation and conclusion The radical S-adenosylmethionine(SAM)aminomutases represent an important pathway for the biosynthesis of p-amino acids.In this study,we report biochemical characterization of BlsG involved in blasticidin S biosynthesis as a radical SAM arginine 2,3-aminomutase.We showed that BlsG acts on both£-arginine and L-lysine with comparable catalytic efficiencies.Similar dual substrate specificity was also observed for the lysine 2,3-aminomutase from Escherichia coli(LAMec).The catalytic efficiency of LAMEc is similar to that of BlsG,but is significantly lower than that of the enzyme from Clostridium subterminale(LAMcs),which acts only on L-lysine rather than on L-arginine.Moreover,we showed that enzymes can be grouped into two major phylogenetic clades,each corresponding to a certain C3 stereochemistry of the P-amino acid product.Our study expands the radical SAM aminomutase members and provides insights into enzyme evolution,supporting a trade-off between substrate promiscuity and catalytic efficiency.