Crystallization of 3-hexulose-6-phosphate synthase

The crystal structures can reveal detailed information about the overall structure, active site structure, and functional mechanism of enzymes. This study focused on the crystallization of 3-hexulose-6-phosphate synthase from Methylomonas aminofaciens 77a, to produce higher resolution crystals for precise structural characterization. 3-Hexulose-6-phosphate synthase is from Methylomonas aminofaciens 77a (EC 4.1.2.43). It belongs to the orotidine 5'-monophosphate decarboxylase superfamily, and acts as a key enzyme for a ribulose-monophosphate cycle of formaldehyde fixation and detoxification. 3-Hexulose-6-phosphate synthase catalyzes the aldol condensation of formaldehyde with D-ribulose-5-phosphate. For the maximum activity, 3-hexulose-6-phosphate synthase requires Mg2+ or Mn2+ as ligands. MaHPS crystallized at the concentration of 7 mg/mL and conditions consisting of 0.2 M MgCl2, 18% PEG 3350 at pH = 7.0.

Re-refinement of Plasmodium falciparum orotidine 5′-monophosphate decarboxylase provides a clearer picture of an important malarial drug target

The development of antimalarial drugs remains a public health priority, and the orotidine 5′-monophosphate decarboxylase from Plasmodium falciparum (PfOMPDC) has great potential as a drug target. The crystallization of PfOMPDC with substrate bound represents an important advance for structure-based drug-design efforts [Tokuoka et al. (2008), J. Biochem. 143, 69–78]. The complex of the enzyme bound to the substrate OMP (PDB entry 2za1) would be of particular utility in this regard. However, re-refinement of this structure of the Michaelis complex shows that the bound ligand is the product rather than the substrate. Here, the re-refinement of a set of three structures, the apo enzyme and two versions of the product-bound form (PDB entries 2za1, 2za2 and 2za3), is reported. The improved geometry and fit of these structures to the observed electron density will enhance their utility in antimalarial drug design.