Specifically methylates cytosine 38 in the anticodon loop of tRNA(Asp). Can also methylate cytosine 38 in tRNA(Glu), albeit to a lower level, but not tRNA(Lys). Pmt1-dependent tRNA methylation is induced by nitrogen limitation and depends on the nutrient-sensing protein kinase sck2. Does not have DNA-methylation activity. cytidine(38) in tRNA + S-adenosyl-L-methionine = 5-methylcytidine(38) in tRNA + H(+) + S-adenosyl-L-homocysteine Constitutively expressed at protein and RNA levels. Belongs to the class I-like SAM-binding methyltransferase superfamily. C5-methyltransferase family. Was originally thought not to have cytosine-5 methyltransferase activity, and this was attributed to the insertion of a Ser residue between the Pro-Cys motif found at the active site of C5 MTases (PubMed:8636983). When this serine is deleted it becomes catalytically active and recognizes and methylates the sequence CC[AT]GG. This was in agreement with S.pombe lacking m5C DNA-methylation. However, it has later been shown that it has tRNA-methyltransferase activity despite this sequence variation (PubMed:23074192).