 Depending on the organism, the capping enzyme is either a monofunctional or bifunctional polypeptide.The guanylyltransferases (Ceg1) of "Saccharomyces cerevisiae" is encoded by the "CEG1" gene and is composed of 459 amino acids (53-kD).The RNA triphosphatase (Cet1) is a separate 549 amino acid polypeptide (80-kD), encoded by the "CET1" gene.