6-Pyruvoyl tetrahydrobiopterin synthase.

What is it about?

6-Pyruvoyl tetrahydrobiopterin synthase (PTPS) catalyses the conversion of dihydroneopterin triphosphate to 6-pyruvoyl tetrahydropterin, the second of the three enzymatic steps in the synthesis of tetrahydrobiopterin from GTP. PH0634, a 13.51 kDa archaeal PTPS homologue from Pyrococcus horikoshii OT3, was overexpressed as native and selenomethionine-substituted protein and the purified protein was crystallized by the oil-microbatch method at 295 K. X-ray diffraction data were collected to 2.1 A resolution from the native crystal using synchrotron radiation at 100 K

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Why is it important?

The PH0634 protein (115 residues) from Pyrococcus horikoshii OT3 shares 37% (36 out of 97 amino acids) sequence identity with the 6-pyruvoyl tetrahydrobiopterin synthase (PTPS) of known structure from rat liver (Nar et al., 1994). PTPS is the second enzyme in the biosynthetic pathway from GTP to tetrahydrobiopterin and catalyses the conversion of dihydroneopterin triphosphate to 6-pyruvoyl tetrahydropterin (Tho ̈ ny et al., 2000). The product of the three-step pathway, tetrahydrobiopterin, is an essential cofactor for several aromatic amino-acid monooxygenases and nitric oxide synthases. The crystal structure of PTPS from rat liver (144 residues) revealed that it functions as a hexamer composed of a pair of trimers arranged in a head-to-head fashion (Nar et al., 1994; Ploom et al., 1999).

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