Structural analyses of enzymes involved in biosynthetic pathways that are present in micro-organisms, but absent from mammals (for example Shikimate pathway) are important in developing anti-microbial drugs. Crystal structure of the Shikimate pathway enzyme, type I 3-dehydroquinate dehydratase (3-DHQase) from the hyperthermophilic bacterium Aquifex aeolicus was solved both as an apo form and in complex with a ligand. The complex structure revealed an interesting structural difference when compared to other ligand-bound-type I 3-DHQases suggesting that closure of the active site loop is not essential for catalysis. This provides new insights into the catalytic mechanism of type I 3-DHQases. (C) 2013 Elsevier Inc. All rights reserved.