Crystallization and preliminary X-ray analysis of pyridoxine 4-oxidase, the first enzyme in pyridoxine degradation pathway I

Vitamin B₆-degradation pathway I has recently been identified in Mesorhizobium loti MAFF303099. Pyridoxine 4-oxidase, an FAD-dependent enzyme, is the first enzyme in this pathway and catalyzes the irreversible oxidation of pyridoxine to pyridoxal. The enzyme was overexpressed in Escherichia coli with a His₆ tag and purified. The recombinant enzyme was crystallized at 277 K by the sitting-drop vapour-diffusion method using PEG 4000 as the precipitant. The crystal, which belonged to space group P2₁2₁2₁ with unit-cell parameters a = 62.38, b = 79.44, c = 136.43 Å, diffracted to 2.2 Å resolution. The calculated V_M value (3.19 Å³ Da^-1) suggested that the asymmetric unit contained one molecule.