Phosphoenolpyruvate carboxykinase (PCK) is a key enzyme involved in the regulation of gluconeogenesis. PCKs from higher animals require guanosine nucleotide for activity. PCK from Corynebacterium glutamicum is also GTP specific. X-ray diffraction data from a C. glutamicum PCK crystal were collected to 2.8 A resolution. The crystals were monoclinic, belonging to space group P2(1), with unit-cell parameters a = 71.7, b = 117.4, c = 161.3 A, beta = 92.9 degrees. The presence of two molecules in the crystallographic asymmetric unit gives a V(M) of 2.5 A(3) Da(-1) and a solvent content of 50.3%.