histamine + S-adenosyl-L-methionine = N(tau)-methylhistamine + S-adenosyl-L-homocysteine + H(+)
histamine + s-adenosyl-l-methionine = n(tau)-methylhistamine + s-adenosyl-l-homocysteine + h(+)
"histamine N-methyltransferase"
"histamine n-methyltransferase"