In mammals, Tyw5 catalyzes hydroxylation of a beta carbon in the lateral acp group of yW72 (the product of Tyw3 enzyme) to form hydroxyl derivative OHyW*. Reaction depends on Fe(II) ion and 2-oxoglutarate (2-OG) as cofactors. Homodimer. Catalytic domain consists of a β-jellyroll fold, a hallmark of the JmjC domains and other Fe(II)/2-OG oxygenases. Compound OHyW* is further transformed by the bifunctional Tyw4 enzyme into the final OHyW (hydroxywybutosine). Hydroxylated yW derivatives are absent in yeast.