Expression, crystallization and preliminary X-ray analysis of rice L-galactose dehydrogenase.

In plants, L-galactose dehydrogenase (L-GalDH) is a key enzyme in the biosynthesis of ascorbic acid (AsA), which is well known as a unique antioxidant compound and a cofactor for many enzymes. L-GalDH catalyses the oxidation of L-galactose to L-galactono-1,4-lactone. Rice L-GalDH was overexpressed in Escherichia coli, purified and crystallized. Diffraction-quality rod-shaped crystals were grown using a sitting-drop vapour-diffusion method. The L-GalDH crystals exhibited the symmetry of space group P21 and diffracted to a resolution of 1.2 Å. The crystals had unit-cell parameters a = 46.8, b = 54.9, c = 56.9 Å, β = 102.3°. On the basis of the Matthews coefficient (VM = 2.1 Å(3) Da(-1), solvent content of 42.3%), it was estimated that one peptide was present in the asymmetric unit.