cytidine(2499) in 23S rRNA + S-adenosyl-L-methionine = 5-methylcytidine(2499) in 23S rRNA + S-adenosyl-L-homocysteine + H(+)
cytidine(2499) in 23s rrna + s-adenosyl-l-methionine = 5-methylcytidine(2499) in 23s rrna + s-adenosyl-l-homocysteine + h(+)