Multisite-specific tRNA:(cytosine-C5)-methyltransferase (EC 2.1.1.202, multisite-specific tRNA:m5C-methyltransferase, TRM4 (gene)) is an enzyme with systematic name S-adenosyl-L-methionine:tRNA (cytosine-C5)-methyltransferase.^[1][2][3][4] This enzyme catalyses the following chemical reaction

(1) S-adenosyl-L-methionine + cytosine³⁴ in tRNA precursor ${\displaystyle \rightleftharpoons }$ S-adenosyl-L-homocysteine + 5-methylcytosine³⁴ in tRNA precursor

(2) S-adenosyl-L-methionine + cytosine⁴⁰ in tRNA precursor ${\displaystyle \rightleftharpoons }$ S-adenosyl-L-homocysteine + 5-methylcytosine⁴⁰ in tRNA precursor

(3) S-adenosyl-L-methionine + cytosine⁴⁸ in tRNA ${\displaystyle \rightleftharpoons }$ S-adenosyl-L-homocysteine + 5-methylcytosine⁴⁸ in tRNA

(4) S-adenosyl-L-methionine + cytosine⁴⁹ in tRNA ${\displaystyle \rightleftharpoons }$ S-adenosyl-L-homocysteine + 5-methylcytosine⁴⁹ in tRNA

The enzyme from Saccharomyces cerevisiae is responsible for complete 5-methylcytosine methylations of yeast tRNA.