tRNA wybutosine-synthesizing protein 5 （TYW5） functions as a component of the wybutosine biosynthesis pathway. Wybutosine is a hyper modified guanosine with a tricyclic base found at the 3’-position closest to the anticodon of eukaryotic phenylalanine tRNA. TYW5 catalyzes the hydroxylation of 7-（a-amino-a-carboxypropyl）wyosine （yW-72） into undermodified hydroxywybutosine （OHyW）. OHyW is a derivative of wybutosine observed in higher eukaryotes.
