Crystallization and preliminary crystallographic studies of pyridoxal kinase from sheep brain

Pyridoxal kinase (ATP:pyridoxal 5'-phosphotransferase; EC 2.7.1.35) is a key enzyme in the transformation of vitamin B₆ to pyridoxal-5'-­phosphate. Pyridoxal-5'-phosphate is the crucial cofactor required by numerous enzymes involved in the metabolism of amino acids and the synthesis of many neurotransmitters. Pyridoxal kinase from sheep brain was crystallized in an orthorhombic form using the hanging-drop vapour-diffusion method with sodium citrate as the precipitant. The crystals belong to space group P2₁2₁2₁, with unit-cell parameters a = 59.8, b = 94.4, c = 128.2 Å, and diffract to a resolution of 2.1 Å. Crystals were transferred into a soaking liquid without citrate and two heavy-atom derivatives were prepared.