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.