Aminotransferases are essential enzymes involved in the central metabolism of all organisms. The la subfamily of aspartate and tyrosine aminotransferases (AATases and TATases) is the best-characterized. grouping, but only eight enzymes from this subfamily, representing relatively little sequence diversity, have been experimentally characterized for substrate specificity (i.e., AATase vs. TATase). Genome annotation, based on this limited dataset, provides tentative assignments for all sequenced members of this subfamily. This procedure is, however, subject to error, particularly when the experimental basis set is limited. To address this problem we cloned twelve additional subfamily lot enzymes from an evolutionarily divergent set. of organisms. Nine were purified to homogeneity after heterologous expression in Escherichia coli in native, intein-tagged or His(6)-tagged forms. The two Saccharomyces cerevisiae isoforms were recombinantly produced in yeast. The effects of the C-terminal tags on expression, purification and enzyme activity are discussed. (c) 2007 Elsevier Inc. All rights reserved.