putrescine + S-adenosyl-L-methionine = N-methylputrescine + S-adenosyl-L-homocysteine + H(+)
putrescine + s-adenosyl-l-methionine = n-methylputrescine + s-adenosyl-l-homocysteine + h(+)
"putrescine N-methyltransferase"
"putrescine n-methyltransferase"