Crystallization of diaminopimelate decarboxylase from Escherichia coli, a stereospecific D-amino-acid decarboxylase

The final step in lysine biosynthesis in bacteria, the conversion of meso-diaminopimelate to L-lysine, is catalyzed by the only known D-­amino-acid decarboxylase, diaminopimelate decarboxylase (DDC). The Escherichia coli DDC has been cloned, overexpressed in E. coli with a carboxy-terminal polyhistidine purification tag and crystallized from lithium sulfate. The protein is intensely yellow, owing to the pyridoxal-5'-phosphate cofactor, and is enzymatically active. Large well ordered crystals, belonging to space group P6₁22 with unit-cell parameters a = b = 98.6, c = 177 Å, make high-resolution X-ray diffraction studies possible to characterize the residues important in stereospecific decarboxylation and reprotonation during catalytic turnover.