3-dehydroquinate dehydratase (EC 4.2.1.10), or dehydroquinase, catalyzes the conversion of 3-dehydroquinate into 3-dehydroshikimate. It is the third step in the shikimate pathway for the biosynthesis of aromatic amino acids from chorismate. Two classes of dehydroquinases exist, known as types I and II. Class-II enzymes are homododecameric enzymes of about 17 Kd. They are found in some bacteria such as actinomycetales [1,2] and some fungi where they act in a catabolic pathway that allows the use of quinic acid as a carbon source. As a signature pattern, we selected a conserved region in the N-terminal section.