Three-dimensional structure at 3.2 Å resolution of the complex of cytosolic aspartate aminotransferase from chicken heart with 2-oxoglutarate

Aspartate aminotransferase (EC 2.6.1.1; L-aspartate: 2-oxoglutarate aminotransferase, AATase) is one of the key enzymes of nitrogen metabolism [ 11. The tissues of vertebrates contain 2 homologous isozymic forms of this enzyme: a cytosolic and a mitochondrial form. Both isoenzymes are dimeric proteins, consisting of 2 identical subunits of Mr 45 000. Currently, X-ray structural investigations are underway of chicken cAATase and mAATase [2-41 and of porcine cAATase [S]. Here, we report studies of the threedimensional structure of chicken cAATase at 3.2 A resolution. The sequence of its peptide chain is known [6].