Crystallization and preliminary X-ray diffraction studies of C-4-form phosphoenolpyruvate carboxylase from maize

Phosphoenolpyruvate carboxylase is a key enzyme in the fixation of atmosphe ric CO2 in C-4 and crassulacean acid metabolism (CAM) plants. The enzyme ca talyzes the irreversible carboxylation of phosphoenolpyruvate to form exalo acetate and inorganic phosphate, the first committed step in the fixation o f external CO2 in these plants. The enzyme has been isolated from maize lea ves and crystallized using the hanging-drop vapour-diffusion method with PE G 8000 as a precipitant at pH 7.5. The crystals belong to space group C222( 1), with unit-cell dimensions a = 160.2, b = 175.6, c = 255.5 Angstrom, and diffract to 3.2 Angstrom resolution.