Locations of the zwf, edd, and eda genes on the Escherichia coli physical map.

The 40.5-min region of the Escherichia coli map contains the zwf gene, which encodes glucose-6-phosphate dehydrogenase, an enzyme of the pentose phosphate pathway, and the edd and eda genes, which encode 6-phosphogluconate dehydratase and 2-keto-3-deoxy-6-phosphogluconate aldolase, respectively, the key enzymes of the Entner-Doudoroff pathway (4). These three genes are tightly linked, and their order with respect to flanking genetic markers has been firmly established by fine-structure mapping (1, 3). Some time ago the zwf, edd, and eda genes were shown to be present on two plasmids from the Clarke-Carbon gene library (8). Recently, the zwf gene was subcloned from pLC3-33 and its nucleotide sequence was determined (7). Likewise, the edd and eda genes were subcloned from