Genes for d-galactarate (gar) and d-glucarate (gud) metabolism in Escherichia coli are organized in three transcriptional units: garD, garPLRK, and gudPD. Two observations suggested a common regulator for the three operons. (i) Their expression was triggered by d-galactarate, d-glucarate, and d-glycerate. (ii) Metabolism of the three compounds was impaired by a single Tn5 insertion mapped in the yaeG gene (proposed name, sdaR), outside the d-galactarate and d-glucarate systems. Expression of the sdaR gene is autogenously regulated.