label: a 5'-end phospho-adenosine-phospho-ribonucleoside in mRNA + FMN + 2 H(+) => a 5'-end FAD-phospho-ribonucleoside in mRNA + H2O
label_lc: a 5'-end phospho-adenosine-phospho-ribonucleoside in mrna + fmn + 2 h(+) => a 5'-end fad-phospho-ribonucleoside in mrna + h2o