Cyclic phosphodiesterase (CPDase, Swiss:O04147) is involved in the tRNA splicing pathway. This protein exhibits a bilobal arrangement of two alpha-beta modules. Two antiparallel helices are found on the outer side of each lobe and frame an antiparallel beta-sheet that is wrapped around an accessible cleft. Moreover, the beta-strands of each lobe interact with the other lobe. The central water-filled cavity houses the enzyme's active site [1].

1: Structure and mechanism of activity of the cyclic phosphodiesterase of Appr>p, a product of the tRNA splicing reaction. Hofmann A, Zdanov A, Genschik P, Ruvinov S, Filipowicz W, Wlodawer A; EMBO J 2000;19:6207-6217. PMID:11080166