Specifically methylates cytosine 38 in the anticodon loop of tRNA(Asp). cytidine(38) in tRNA + S-adenosyl-L-methionine = 5-methylcytidine(38) in tRNA + H(+) + S-adenosyl-L-homocysteine Highly expressed in thymus, testis, and at much lower levels in spleen, lung, brain, heart, kidney, liver, skeletal muscle and embryonic stem cells. Mice are viable and fertile, but show loss of 5-methylcytidine(38) in tRNA (PubMed:21183079, PubMed:22885326). Mice lacking both Nsun2 and Trdmt1 display a complete loss of cytosine-C5 tRNA methylation, leading to development defects and impaired cellular differentiation causing lethality before P3 (PubMed:22885326). Belongs to the class I-like SAM-binding methyltransferase superfamily. C5-methyltransferase family.