label: N(alpha)-methyl-L-tryptophan + S-adenosyl-L-methionine = N(alpha),N(alpha)-dimethyl-L-tryptophan + S-adenosyl-L-homocysteine + H(+)
label_lc: n(alpha)-methyl-l-tryptophan + s-adenosyl-l-methionine = n(alpha),n(alpha)-dimethyl-l-tryptophan + s-adenosyl-l-homocysteine + h(+)