TRNA (cytosine34-C5)-methyltransferase (, hTrm4 Mtase, hTrm4 methyltransferase, hTrm4 (gene), tRNA:m5C-methyltransferase) is an enzyme with systematic name S-adenosyl-L-methionine:tRNA (cytosine34-C5)-methyltransferase. This enzyme catalyses the following chemical reaction
The human enzyme is specific for C<sup>5</sup>-methylation of cytosine<sup>34</sup> in tRNA precursors.