tRNA (guanine37-N1)-methyltransferase (EC 2.1.1.228, TrmD, tRNA (m1G37) methyltransferase, transfer RNA (m1G37) methyltransferase, Trm5p, TRMT5, tRNA-(N1G37) methyltransferase, MJ0883 (gene)) is an enzyme with systematic name S-adenosyl-L-methionine:tRNA (guanine37-N1)-methyltransferase. This enzyme catalyses the following chemical reactionS-adenosyl-L-methionine + guanine37 in tRNA S-adenosyl-L-homocysteine + N1-methylguanine37 in tRNA