Enzymatic synthesis of methyl derivatives of L-tryptophan selectively labeled with hydrogen isotopes

We report the enzymatic synthesis of the derivatives of L-tryptophan methylated in indole moiety and labeled with deuterium and tritium in the 2-position of side chain. For kinetic studies twelve isotopomers, i.e., 1'-methyl-[2-²H]-, 1'-methyl-[2-³H]-, 1'-methyl-[2-²H/³H]-, 2'-methyl-[2-²H]-, 2'-methyl-[2-³H]-, 2'-methyl-[2-²H/³H]-, 5'-methyl-[2-²H]-, 5'-methyl-[2-³H]-, 5'-methyl-[2-²H/³H]-, 7'-methyl-[2-²H]-, 7'-methyl-[2-³H]-, and 7'-methyl-[2-²H/³H]-L-tryptophan are obtained by the enzymatic coupling of the appropriate methylated indole moiety with S-methyl-L-cysteine catalyzed by the enzyme tryptophanase.