S-adenosyl-L-methionine-dependent methyltransferase that mediates N(3)-methylcytidine modification of residue 32 of the tRNA anticodon loop of tRNA(Ser), including tRNA(Ser)(UGA) and tRNA(Ser)(GCU) (PubMed:32923617, PubMed:34922197, PubMed:34268557, PubMed:34862464). Interaction with SARS1/SerRS is required for N(3)-methylcytidine methylation (PubMed:34268557). cytidine(32) in tRNA(Ser) + S-adenosyl-L-methionine = H(+) + N(3)-methylcytidine(32) in tRNA(Ser) + S-adenosyl-L-homocysteine kcat is 7200 min(-1) for tRNA(Ser) (PubMed:34922197). kcat is 7100 min(-1) for S-adenosyl-L-methionine (PubMed:34922197). Monomer (PubMed:34862464). Interacts with SARS1/SerRS; interaction is mediated via tRNA(Ser) and is required for N(3)-methylcytidine methylation (PubMed:28655767, PubMed:34268557). Belongs to the methyltransferase superfamily. METL family. Contaminating sequence. Potential poly-A sequence.