Purification, crystallization and preliminary X-ray diffraction analysis of a novel keto-deoxy-D-galactarate (KDG) dehydratase from Agrobacterium tumefaciens.

D-galacturonic acid is the main component of pectin. It could be used to produce affordable renewable fuels, chemicals and materials through biotechnical conversion. Keto-deoxy-D-galactarate (KDG) dehydratase is an enzyme in the oxidative pathway of D-galacturonic acid in Agrobacterium tumefaciens (At). It converts 3-deoxy-2-keto-L-threo-hexarate to α-ketoglutaric semialdehyde. At KDG dehydratase was crystallized by the hanging-drop vapour-diffusion method. The crystals belonged to the monoclinic space group C2, with unit-cell parameters a = 169.1, b = 117.8, c = 74.3 Å, β = 112.4° and an asymmetric unit of four monomers. X-ray diffraction data were collected to 1.9 Å resolution using synchrotron radiation. The three-dimensional structure of At KDG dehydratase will provide valuable information on the function of the enzyme and will allow it to be engineered for biorefinery-based applications.