label: a 5'-end phospho-ribonucleoside in mRNA + diphosphate + H(+) => a 5'-end triphospho-ribonucleoside in mRNA + H2O
label_lc: a 5'-end phospho-ribonucleoside in mrna + diphosphate + h(+) => a 5'-end triphospho-ribonucleoside in mrna + h2o