Crystal Structure of Brain Pyridoxal Kinase, a Novel Member of the

The three-dimensional structures of brain pyridoxal kinase and its complex with the nucleotide ATP have been elucidated in the dimeric form at 2.1 and 2.6 Å, respectively. Results have shown that pyridoxal kinase, as an enzyme obeying random sequential kinetics in catalysis, does not possess a lid shape structure common to all kinases in the ribokinase superfamily. This finding has been shown to be in line with the condition that pyridoxal kinase binds substrates with variable sizes of chemical groups at position 4 of vitamin B6 and its de-rivatives. In addition, the enzyme contains a 12-residue peptide loop in the active site for the prevention of premature hydrolysis of ATP. Conserved amino acid res-idues Asp118 and Tyr127 in the peptide loop could be moved to a position covering the nucleotide after it