L-histidine Nalpha-methyltransferase; dimethylhistidine N-methyltransferase; dimethylhistidine methyltransferase; histidine-alpha-N-methyltransferase; S-adenosyl-L-methionine:alpha-N,alpha-N-dimethyl-L-histidine alpha-N-methyltransferase; S-adenosyl • • •