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 Additional isoforms seem to exist. Ubiquitous. Higher expression in testis, ovary and thymus and at much lower levels in spleen, prostate, colon, small intestine, and peripheral blood leukocytes. Belongs to the class I-like SAM-binding methyltransferase superfamily. C5-methyltransferase family.