S-adenosyl-L-methionine-dependent methyltransferase that mediates N(3)-methylcytidine modification of residue 32 of the tRNA anticodon loop of tRNA(Thr)(UGU) and tRNA(Arg)(CCU). N(3)-methylcytidine methylation by mettl2a requires the N6-threonylcarbamoylation of tRNA (t6A37) by the EKC/KEOPS complex as prerequisite. cytidine(32) in tRNA(Thr) + S-adenosyl-L-methionine = H(+) + N(3)-methylcytidine(32) in tRNA(Thr) + S-adenosyl-L-homocysteine cytidine(32) in tRNA(Arg)(CCU) + S-adenosyl-L-methionine = H(+) + N(3)-methylcytidine(32) in tRNA(Arg)(CCU) + S-adenosyl-L-homocysteine Monomer. Belongs to the methyltransferase superfamily. METL family.