What is the X in X-mas?
transferase trans·fer·ase (trāns'fə-rās', -rāz')
Any of various enzymes that catalyze the transfer of a chemical group, such as a phosphate or an amine, from one molecule to another.
any one of a class of more than 450 enzymes that catalyze the transfer of various chemical groups (other than hydrogen) from one compound to another. Transaminases, for example, catalyze the transfer of an amino group (NH2) from an amino acid to an a-keto acid. Phosphate, methyl (CH3), and sulfur-containing groups are among the other groups transferred by the action of these enzymes. For the large and important group of enzymes that catalyze the transfer of hydrogen, see oxidoreductase.