GMP-PDE delta subunit was originally identified as a fourth subunit of rod-specific cGMP phosphodiesterase (PDE)(EC:3.1.4.35). The precise function of PDE delta subunit in the rod specific GMP-PDE complex is unclear. In addition, PDE delta subunit is not confined to photoreceptor cells but is widely distributed in different tissues. PDE delta subunit is thought to be a specific soluble transport factor for certain prenylated proteins and Arl2-GTP a regulator of PDE-mediated transport [1].

1: The complex of Arl2-GTP and PDE delta: from structure to function. Hanzal-Bayer M, Renault L, Roversi P, Wittinghofer A, Hillig RC; EMBO J 2002;21:2095-2106. PMID:11980706